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height="7.682638888888889in"}

> **AHRQ Quality Indicators**
>
> **Patient Safety Indicators:**
>
> **Software Documentation,**
>
> **Version 2.1, Revision 2**
>
> **SPSS**

Department of Health and Human Services\
Agency for Healthcare Research and Quality\
[http://www.qualityindicators.ahrq.gov](http://www.qualityindicators.ahrq.gov/)

March 2003

AHRQ Pub. No. 03-R205

Revision 2 (October 22, 2004)

**Citation**

AHRQ Quality Indicators \-- Patient Safety Indicators: Software
Documentation, Version 2.1 - SPSS. Rockville, MD: Agency for Healthcare
Research and Quality, 2003. Revision 2 (October 22, 2004) AHRQ
Pub.03-R205

# Abstract

The value of information on health care quality has never been so widely
recognized; yet many organizations lack the resources and/or expertise
to build a quality information program from the ground up. Recognizing
this, the AHRQ Quality Indicators were developed specifically to meet
the short-term needs for information on health care quality using
standardized, user-friendly methods and existing sources of data.

This module of the AHRQ Quality Indicators was designed to capitalize on
the availability of administrative data on inpatient stays to produce
information for Patient Safety Indicators (PSIs). These indicators
capture potentially preventable complications and iatrogenic events for
patients treated in hospitals. They can be used as a screening tool for
problems that patients experience as a result of exposure to the
healthcare system and that are likely amenable to prevention by changes
at the system or hospital level.

This document is the software documentation for the Patient Safety
Indicators software Version 2.1, Revision 2, which is provided on the
AHRQ Web site. The software was developed in SPSS, for use on a personal
computer. By making this tool available, we hope to assist others in
producing information on health care quality more cost effectively.

Details on the development of the Inpatient Quality Indicators can be
found in \"Guide to Patient Safety Indicators.\"

# Acknowledgments

This product is based on the work of many individuals who contributed to
its development and testing.

The following staff from the **Evidence-based Practice Center (EPC) at
UCSF-Stanford** performed the evidence review, facilitated clinician
reviews, completed the empirical evaluation, and created the programming
code and technical documentation for the new Patient Safety Indicators:

  ----------------------------------- -----------------------------------
  ***Core Project Team***             ***Other Contributors***

  Kathryn M. McDonald, M.M.           Kaveh G. Shojania, M.D. (UCSF)
  (Stanford)                          

  Jeffrey Geppert, J.D. (Stanford)    Bradford Duncan M.D. (Stanford)

  Sheryl M. Davies, M.A. (Stanford)   Angela Hansen, B.A. (Stanford)

  Patrick Romano, M.D., M.P.H.        
  (UC-Davis)                          
  ----------------------------------- -----------------------------------

The following staff from **Social & Scientific Systems**, **Inc.**,
developed this software product, documentation, and guide:

  ----------------------------------- -----------------------------------
  ***Programmers***                   ***Technical Writer***

  Leif Karell                         Patricia Burgess

  Kathy McMillan                      

  Fred Rohde                          ***Graphics Designer***

                                      Laura Spofford
  ----------------------------------- -----------------------------------

Contributors from the **Agency for Healthcare Research and Quality**:

  ----------------------------------- -----------------------------------
  Anne Elixhauser, Ph.D.              H. Joanna Jiang, Ph.D.

  Marlene Miller, M.D., M.Sc.         Margaret Coopey, R.N., M.G.A,
                                      M.P.S.

  Denise Remus, Ph.D., R.N.           
  ----------------------------------- -----------------------------------

  ------------------------ --------- -------------- ---------- ------------------------
  Support efforts,                                             
  including refinement and                                     
  enhancement of the AHRQ                                      
  Quality Indicators and                                       
  related products, are                                        
  provided by the Support                                      
  for Quality Indicators                                       
  contract team.                                               

                                                               

  The following                                                
  individuals from                                             
  **Stanford University,                                       
  University of California                                     
  (UC)** and **Battelle                                        
  Memorial Institute**                                         
  constitute the Support                                       
  for Quality Indicators                                       
  core team:                                                   

                                                               

  Sheryl M. Davies, M.A.   Mark                                Rajin Mangru, B.S.
                           Gritz,                              
                           Ph.D.                               

  Bruce Ellis, M.S.        Greg                                Kathryn M. McDonald,
                           Hubert,                             M.M.
                           B.S.                                

  Jeffrey Geppert, J.D.    Elaine                              Patrick Romano, M.D.,
                           Keller,                             M.P.H
                           M.Ed.                               

                                                               

  The **Agency for                                             
  Healthcare Research and                                      
  Quality** Support for                                        
  Quality Indicators team                                      
  includes:                                                    

  Denise Remus, Ph.D.,                              Mary B.    
  R.N., Project Officer                             Haines,    
                                                    Contract   
                                                    Officer    
  ------------------------ --------- -------------- ---------- ------------------------

> We also wish to acknowledge the invaluable contribution of the
> clinical panelists and the peer reviewers of the evidence report; and
> the beta-testers of the software products.

Table of Contents

Abstract [i](#abstract)

Acknowledgments [ii](#acknowledgments)

Introduction [1](#introduction)

Components of the Patient Safety Indicators Module
[1](#components-of-the-patient-safety-indicators-module)

Quick Reference [2](#quick-reference)

Processing Steps [2](#processing-steps)

Patient Safety Indicator Module Details
[5](#patient-safety-indicator-module-details)

Background [7](#background)

Data Elements and Coding Conventions
[8](#data-elements-and-coding-conventions)

Input for the AHRQ Quality Indicators
[8](#input-for-the-ahrq-quality-indicators)

Coding of Diagnoses, Procedures, DRGs and MDCs
[10](#coding-of-diagnoses-procedures-drgs-and-mdcs)

Use of External Cause of Injury Codes
[10](#use-of-external-cause-of-injury-codes)

Missing Values [14](#missing-values)

Treatment of Missing Data [14](#treatment-of-missing-data)

User Options [15](#user-options)

Producing Patient Safety Indicator Rates: Processing Steps
[16](#producing-patient-safety-indicator-rates-processing-steps)

1\. Identify outcomes in inpatient records
[16](#identify-outcomes-in-inpatient-records)

2\. Identify populations at risk [16](#identify-populations-at-risk)

3\. Calculate observed (raw) Patient Safety Indicator rates
[16](#calculate-observed-raw-patient-safety-indicator-rates)

4\. Risk-adjust the Patient Safety Indicator Rates. Provider PSIs only.
[17](#risk-adjust-the-patient-safety-indicator-rates.-provider-psis-only.)

5\. Create MSX Smoothed Rates. Provider PSIs Only
[17](#create-msx-smoothed-rates.-provider-psis-only)

Program Descriptions [18](#program-descriptions)

Program 1: Run PSSPS1 [18](#program-1-run-pssps1)

Program 2: Run PSSPSP2 [19](#program-2-run-psspsp2)

Program 3: Run PSSPSP3 [22](#program-3-run-psspsp3)

Program 4: Run PSSPSA2 [23](#program-4-run-psspsa2)

Reviewing the Printed Output [26](#reviewing-the-printed-output)

PSSPS1 [26](#pssps1)

PSSPSP2 [26](#psspsp2)

PSSPSP3 [27](#psspsp3)

PSSPSA2 [28](#psspsa2)

Interpreting the Results [30](#interpreting-the-results)

Using Indicators in Combination [30](#using-indicators-in-combination)

Observed Means [30](#observed-means)

Risk-adjusted Rates. Provider PSIs Only
[31](#risk-adjusted-rates.-provider-psis-only)

MSX Smoothed rates (Optional). Provider PSIs Only
[31](#msx-smoothed-rates-optional.-provider-psis-only)

Comparing Observed, Risk-adjusted and Smoothed Rates. Provider PSIs Only
[33](#comparing-observed-risk-adjusted-and-smoothed-rates.-provider-psis-only)

Comparing Observed Rates with Risk-adjusted Rates
[34](#comparing-observed-rates-with-risk-adjusted-rates)

Comparing Risk-adjusted Rates with Smoothed Rates (Optional)
[34](#comparing-risk-adjusted-rates-with-smoothed-rates-optional)

Confidence Intervals [35](#confidence-intervals)

Computing Expected Rates (Optional)
[35](#computing-expected-rates-optional)

Benchmark Timings [36](#benchmark-timings)

User Support and Information [36](#user-support-and-information)

Appendix A: Log of Revisions to PSI Documentation and Software Version
2.1, Revision 2
[A-1](#appendix-a-log-of-revisions-to-psi-documentation-and-software-version-2.1-revision-2)

Appendix B: ICD-9-CM and DRG Coding Updates in PSI Release Version 2.1,
Revision 2
[B-1](#appendix-b-icd-9-cm-and-drg-coding-updates-in-psi-release-version-2.1-revision-2)

**List of Figures**

[Figure 1. Processing Steps for the Patient Safety Indicators - Provider
3](#__RefHeading___Toc85945147)

[Figure 2. Processing Steps for the Patient Safety Indicators - Area
4](#__RefHeading___Toc85945148)

**List of Tables**

Table 1. Patient Safety Indicator (PSI) Variables
[5](#__RefHeading___Toc85945149)

Table 2. Prefixes for the Patient Safety Indicator (PSI) Variables
[6](#__RefHeading___Toc85945150)

Table 3. Patient Safety Module Contents [6](#__RefHeading___Toc85945151)

Table 4. Data Elements and Coding Conventions
[11](#__RefHeading___Toc85945152)

Table 5. Treatment of Missing Data Elements
[14](#__RefHeading___Toc85945153)

Table 6. PSSPSP2 Aggregation Possibilities
[21](#__RefHeading___Toc85945154)

Table 7. PSSPSA2 Aggregation Possibilities
[25](#__RefHeading___Toc85945155)

**AHRQ Quality Indicators, SPSS Software Documentation, Version 2.1,
Revision 2: Patient Safety Indicators**

# Introduction

This documentation describes the software for implementing the Patient
Safety Indicator (PSI) module of the AHRQ Quality Indicators Version
2.1, Revision 2 and highlights features of the analytic approach of
particular interest to new users. Detailed information about the Patient
Safety Indicators (PSI) is contained in the companion document "*Guide
to Patient Safety Indicators"*[^1], which includes information about the
development of the indicators and their definitions.

The software consists of a series of computer programs that:

-   Assign and calculate PSIs from hospital discharge abstracts or UB
    (uniform billing) claims data.

-   Print PSI results in SPSS format which can be converted to a word
    processing, spreadsheet, or graphics format, at the user\'s option.

-   Create risk-adjusted rates that adjust for case mix differences.

-   Create smoothed (i.e., reliability-adjusted) rates that reduce
    fluctuations over time due to random variation.

This documentation includes:

-   A discussion of the data elements necessary to produce the AHRQ PSIs
    and the uniform coding conventions recommended for those elements.

-   Descriptions of the PSI processing steps in non-technical language.

-   Detailed descriptions of the functions of each PSI SPSS program.

***Critical user information is highlighted with this symbol:***
![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}

# Components of the Patient Safety Indicators Module

As shown in Table 3 on page [Error: Reference source not
found](#module_contents_table), the Patient Safety Indicators module
consists of four SPSS programs and six ASCII text files that contain
auxiliary data. These programs and text files are described in the
subsequent sections of this document. The programs were developed for
use in Statistical Package for the Social Sciences (SPSS)[^2], version
10.0 or higher, on a Windows personal computer.

A note on the naming conventions for the Patient Safety Indicator (PSI)
module programs. Most programs have names of the form PSSPSi, PSSPSAi,
or PSSPSPi. The first two characters "PS" of the program name indicate a
Patient Safety Indicators program, to distinguish it from other modules
that have been released from AHRQ. The next three characters of the
program name are "SPS" and are present to distinguish the program from
the SAS versions of the software. In the programs that are specific to
either Area or Provider Indicators, the sixth character of the program
name is either "A" or "P". The sixth character is an "A" if it is for
the production of Area indicator rates that use county or Metropolitan
Statistical Area (MSA) area populations as denominators. The sixth
character is a "P" if it is a program that is for the production of
Provider Indicator rates that use subsets of the hospital discharge
population. The last character (i) of the variable name designates the
number of the specific program.

# Quick Reference

The subsequent four pages are intended to serve as a quick reference to
assist in reading this documentation and in reviewing the Patient Safety
Indicator (PSI) module outputs. Processing steps are shown first (Figure
1 and Figure 2) followed by a listing of the module indicator variables
(Table 1), variable prefixes (Table 2), and module contents (Table 3).
One suggestion is to print these pages in duplex mode on two sheets of
paper so that they can then be easily referred to as the need arises.

## Processing Steps

Figure 1 shows processing steps for the Patient Safety Indicators -
[Provider]{.underline}, while Figure 2 shows steps for the Patient
Safety Indicators - [Area]{.underline}.

[]{#__RefHeading___Toc85945147 .anchor}Figure 1. Processing Steps for
the Patient Safety Indicators - [Provider]{.underline}

![](media/image3.jpeg){width="6.501388888888889in"
height="8.027083333333334in"}

NOTE: Each of the SPSS Programs in Figure 1 incorporates the
CONTROL_PSI.SPSS program, which contains code the user **must** modify
in order to run the PSI software. The **modifications** include such
items as specifying the name and location of the input data set, the
population data set, and the output data set.

[]{#__RefHeading___Toc85945148 .anchor}Figure 2. Processing Steps for
the Patient Safety Indicators - [Area]{.underline}

![](media/image4.jpeg){width="5.565277777777778in"
height="6.991666666666666in"}

## Patient Safety Indicator Module Details

The following tables list the module indicator variables (Table 1),
variable prefixes (Table 2), and module contents (Table 3).

[]{#__RefHeading___Toc85945149 .anchor}Table 1. Patient Safety Indicator
(PSI) Variables

+---------+------------------------------------------------------------+
| **PSI** | **Indicator**                                              |
|         |                                                            |
| **n     |                                                            |
| umber** |                                                            |
+---------+------------------------------------------------------------+
| Patient |                                                            |
| Safety  |                                                            |
| Indic   |                                                            |
| ators - |                                                            |
| P       |                                                            |
| rovider |                                                            |
+---------+------------------------------------------------------------+
| 1       | Complications of anesthesia\*                              |
+---------+------------------------------------------------------------+
| 2       | Death in low mortality DRGs^a^                             |
+---------+------------------------------------------------------------+
| 3       | Decubitus ulcer\*                                          |
+---------+------------------------------------------------------------+
| 4       | Failure to rescue                                          |
+---------+------------------------------------------------------------+
| 5       | Foreign body left during procedure\*                       |
+---------+------------------------------------------------------------+
| 6       | Iatrogenic pneumothorax\*                                  |
+---------+------------------------------------------------------------+
| 7       | Selected infections due to medical care\*                  |
+---------+------------------------------------------------------------+
| 8       | Postoperative hip fracture\*                               |
+---------+------------------------------------------------------------+
| 9       | Postoperative hemorrhage or hematoma\*                     |
+---------+------------------------------------------------------------+
| 10      | Postoperative physiologic and metabolic derangements\*     |
+---------+------------------------------------------------------------+
| 11      | Postoperative respiratory failure\*                        |
+---------+------------------------------------------------------------+
| 12      | Postoperative pulmonary embolism or deep vein thrombosis\* |
+---------+------------------------------------------------------------+
| 13      | Postoperative sepsis\*                                     |
+---------+------------------------------------------------------------+
| 14      | Postoperative wound dehiscence\*                           |
+---------+------------------------------------------------------------+
| 15      | Accidental puncture or laceration\*                        |
+---------+------------------------------------------------------------+
| 16      | Transfusion reaction\*                                     |
+---------+------------------------------------------------------------+
| 17      | Birth trauma -- injury to neonate                          |
+---------+------------------------------------------------------------+
| 18      | Obstetric trauma -- vaginal with instrument                |
+---------+------------------------------------------------------------+
| 19      | Obstetric trauma -- vaginal without instrument             |
+---------+------------------------------------------------------------+
| 20      | Obstetric trauma -- cesarean section                       |
+---------+------------------------------------------------------------+
| 27      | Obstetric trauma with 3^rd^ degree -- vaginal with         |
|         | instrument\*                                               |
+---------+------------------------------------------------------------+
| 28      | Obstetric trauma with 3^rd^ degree -- vaginal without      |
|         | instrument\*                                               |
+---------+------------------------------------------------------------+
| 29      | Obstetric trauma with 3^rd^ degree -- cesarean section\*   |
+---------+------------------------------------------------------------+
| Patient |                                                            |
| Safety  |                                                            |
| Indic   |                                                            |
| ators - |                                                            |
| Area    |                                                            |
+---------+------------------------------------------------------------+
| 21      | Foreign body left during procedure                         |
+---------+------------------------------------------------------------+
| 22      | Iatrogenic pneumothorax                                    |
+---------+------------------------------------------------------------+
| 23      | Selected infections due to medical care                    |
+---------+------------------------------------------------------------+
| 24      | Postoperative wound dehiscence                             |
+---------+------------------------------------------------------------+
| 25      | Accidental puncture or laceration                          |
+---------+------------------------------------------------------------+
| 26      | Transfusion reaction                                       |
+---------+------------------------------------------------------------+

a PSI 2 is reported as a single measure, but is also stratified into
medical (adult and pediatric), surgical (adult and pediatric), obstetric
and psychiatric DRGs.

\* These PSI were modified (PSIs 1, 3, 5, 6, 7, 8, 9, 10, 11, 12, 13,
14, 15, 16) or added (PSIs 27, 28, 29) in version 2.1, revision 2.

[]{#__RefHeading___Toc85945150 .anchor}Table 2. Prefixes for the Patient
Safety Indicator (PSI) Variables

  ------------ ------------------------------- --------------- ---------------
  **Prefix**   **Contents**                    **Examples**    

                                               **Provider      **Area
                                               Indicator \#    Indicator\
                                               8,\             \# 23,\
                                               Postoperative   Infection Due
                                               Hip Fracture**  to Medical
                                                               Care**

  T            Inpatient numerator (top)       TPPS08          TAPS23

  P            Population denominator (pop)    PPPS08          PAPS23

  O            Observed Rate                   OPPS08          OAPS23

  R            Risk-adjusted Rate              RPPS08          RAPS23

  S            Smoothed Rate                   SPPS08          SAPS23

  E            Expected Rate                   EPPS08          EAPS23
  ------------ ------------------------------- --------------- ---------------

[]{#__RefHeading___Toc85945151 .anchor}Table 3. Patient Safety Module
Contents

  ------------------------------------ ----------------------------------
  **SPSS programs**                    **ASCII text files †**

  PSSPS1.SPS                           QICTY97.TXT

  PSSPSP2.SPS                          QICTY98.TXT

  PSSPSP3.SPS                          QICTY99.TXT

  PSSPSA2.SPS                          QICTY00.TXT

                                       QICTY01.TXT

                                       QICTY02.TXT

                                       COVPSP00.TXT

                                       MSXPSP_0.TXT
  ------------------------------------ ----------------------------------

† The ASCII text files are data files provided with the Patient Safety
module and are necessary for the programs to run. There is no need to
convert these files to SPSS format for use with the software.

# Background 

The Patient Safety Indicator module contains 29 indicators that reflect
the quality of care inside hospitals. These indicators serve as flags
for potential quality problems rather than definitive measures of
quality of care. The indicators include two groups of measures based on
hospital stays.

1.  There are 23 **Provider-based** Patient Safety Indicators for
    medical conditions and surgical procedures that have been shown to
    have complication/adverse event rates that vary substantially across
    institutions and for which evidence suggests that high
    complication/adverse event rates may be associated with deficiencies
    in the quality of care. These indicators are measured as
    rates---number of complications / adverse events divided by the
    number of admissions for the procedure or condition. The
    Provider-based Indicators include only those cases where a secondary
    diagnosis code flags a potentially preventable complication.

Eight of these indicators are for surgical discharges, eight are for
either medical or surgical discharges, and seven are for obstetric
discharges. Six of the Provider-based Patient Safety Indicators (PSIs 8,
9, 10, 11, 12, 14), incorporate information about when procedures were
performed (relative to the admission date) if this information is
available. Note, however, that if the day of procedure information is
missing, the computed rates for these indicators will be slightly lower
than if the information was available. Admission type is used by four of
the PSIs: Postoperative physiologic and metabolic derangements,
Postoperative respiratory failure, Postoperative sepsis, and Birth
trauma (PSIs 10, 11, 13, and 17), to identify elective surgeries and
newborn admissions.

Note that PSI 2 (Death in Low Mortality DRGs) is reported as a single
provider level measure (observed and risk-adjusted). A single measure is
necessary to insure adequate reliability of the provider level rates by
pooling an infrequent event over a large group of patients. However, the
denominator for the indicator is very heterogeneous, and the mortality
rate among the low mortality DRGs varies by DRG type. For instance,
adult medical DRGs account for about 60% of the deaths, although they
account for only 25% of the discharges in the denominator. Conversely,
obstetric DRGs account for about 5% of the deaths and 45% of discharges
in the denominator. Users should compare the observed rate to the
risk-adjusted rate, which accounts for differences among hospitals in
patient case-mix (i.e., age, gender, DRG and co morbidities). For
example, a hospital may have a high Death in Low Mortality DRG observed
rate only because the hospital has a higher-than-average share of adult
medical DRGs. However, in order to further assist users in understanding
the basis of the Low Mortality DRG rate, and in identifying the
subpopulation of patients that may require further analysis, the
software also calculates eight discharge level Low Mortality DRG
measures by DRG type: medical (adult and pediatric), surgical (adult and
pediatric -- with and without an OR procedure), obstetric and
psychiatric DRGs. Although all the deaths identified by this measure are
potentially preventable, hospitals could decide to focus their attention
on those subpopulations either with the highest share of deaths (e.g.
adult medical DRGs) or with the least likely deaths (e.g. obstetric
DRGs).

2\. There are six **Area-based** Patient Safety Indicators, where
geographic areas can be defined at the MSA (Metropolitan Statistical
Area) level for urban areas and at the county level for rural areas or
by county for all areas. MSAs are defined in terms of entire counties,
which include the county (or counties) that contain the largest city and
any adjacent counties that have at least 50 percent of their population
in the urbanized area surrounding the largest city. In New England, the
MSAs are defined in terms of cities and towns rather than counties. The
MSA definitions in this software are based on the standards effective
June 30, 1999.

These indicators are identical to Provider-based Indicators, except that
the numerator uses principal diagnosis in addition to secondary
diagnoses in order to capture all cases of the complication, and not
only those that develop during a given hospital admission.

The 29 indicators in the PSI module are listed in Table 1 on page
[5](#__RefHeading___Toc85945149). See also Appendix A of the "*Guide to
Patient Safety Indicators"*
(<http://www.qualityindicators.ahrq.gov/psi_download.htm>) for the
definition of each indicator. Note that PSI 2 (for death in low
mortality DRGs) is reported as a single measure, but also has eight
sub-indicators for medical (adult and pediatric -- with and without an
OR procedure), obstetric and psychiatric DRGs.

The data required for measuring these indicators come from hospital
discharge abstracts or billing claims (administrative data) which are
readily available within hospitals or from many state data
organizations. The residential population data for the six area-based
utilization indicators are from the U.S. Census Bureau.

The software generates observed rates for the area-based patient safety
indicators and observed, risk-adjusted, smoothed (i.e.,
reliability-adjusted) and expected rates for all Provider-based
Indicators. Observed rates are the raw rates. Risk-adjusted and expected
rates are derived from applying the average case mix and rates of a
baseline file that reflects a large proportion of the U.S. hospitalized
population. Smoothed rates are estimates with removal of fluctuations
over time due to random variation. The observed rates for the area PSI
are extremely low, and as a result age-sex adjustments are not
necessary.

For information about how these indicators were identified, see the
"*Guide to the Patient Safety Indicators."*
(<http://www.qualityindicators.ahrq.gov/psi_download.htm>)

# Data Elements and Coding Conventions

## Input for the AHRQ Quality Indicators

The PSI software was written to process data from discharge data
abstracts that contain information about hospital stays. The specific
data elements that are needed for the PSI software are listed in Table
4. The PSI module was tested on data from the AHRQ Healthcare Cost and
Utilization Project (HCUP). HCUP is an ongoing Federal-State-private
collaboration to build uniform databases from administrative
hospital-based data collected by State data organizations and hospital
associations. Additional information on HCUP is available at the website
<http://www.ahrq.gov/data/hcup>.

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*The input data files for the Patient Safety Indicators software must be
in SPSS format.*

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*It is strongly recommend that users recode data elements in their input
files to be consistent with the coding expected by the software. We do
not recommend making changes to the Patient Safety Indicators software.
For example, recoding the SEX data element in the input file to be
consistent with the coding described in Table 4 (i.e., 1 for male and 2
for female) should be done rather than attempting to modify all uses of
the Sex data element in the PSI programs.*

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*Not every value for every data element is referenced by the PSI
software. For example, only two of the discharge disposition (DISP) data
elements values are used in the software (DISP value "2" for short-term
hospital and value "20" for died in the hospital). However, the complete
set of standardized values is included, based on HCUP specifications, to
assist users of the uniform HCUP data files.*

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*Four of the indicators (PSIs 10, 11, 13, and 17) use admission type
(ATYPE) to identify elective surgeries and newborn admissions. If
admission type (ATYPE) is not available in the user's data, the user may
want to evaluate other data in the file to create a proxy to identify
elective and newborn admission types.*

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*To minimize internal changes to the software, all required elements
should be present in the input data file. If a required element is not
available, a dummy element should be provided. Failure to provide a
dummy element will result in errors during the execution of the PSI
programs.*

### 

The data elements listed in Table 4 are those required for the input
files of both SAS and SPSS. When a variable is not required for the
program the notation "Not used by the QI program" will be present in the
Comments column. The SAS program will still run if these variables are
not present, however, the SPSS program will not run correctly.
Standardizing the variables and data values in the input data file will
be helpful for users who have access to both statistical software
packages as well as users working to standardize their input file
specifications for use with any of the AHRQ QI software modules.

The data element HOSPSTCO provides flexibility for users to calculate
the area PSIs by provider location or by patient residence. If the user
wants to calculate the PSIs using the population associated with the
provider location as the denominator, the values for this variable
should be the individual provider FIPS[^3] state/county codes. If the
user wants to calculate the area PSIs based on the population of the MSA
region or county associated with the patient residence, the values for
this variable should be the FIPS state/county code associated with each
individual patient's place of residence.

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*If the provider FIPS code is used in HOSPSTCO, users should be aware
that rates may be biased for hospitals which serve as regional referral
centers. These hospitals are likely to treat patients from outside the
MSA, county or even the state in which the facility is located.*

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*Certain independent cities (Baltimore City, Carson City and St. Louis
City), and areas within Hawaii and Virginia, are assigned to different
area groupings in the Modified FIPS categories as compared to the U.S.
Census Bureau groupings. The AHRQ QI software uses the Modified FIPS
code assignment of these areas. Failure to use the Modified FIPS codes
assignment will result in the use of incorrect denominator estimates for
Area Indicators.*

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*Using the patient FIPS state/county code for analysis may more
accurately reflect the true population at risk.*

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*It is possible that some records in the input data file may be missing
the patient FIPS code. Users should be aware that any records with
missing values (in the HOSPSTCO data field) are excluded from the
calculations of observed, risk-adjusted and smoothed PSI area rates.
They will be included in the output from the first program (PSSPS1).*

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*The software will generate area PSI rates for each county included in
the HOSPSTCO data field. Users are encouraged to limit cases in their
input file to those patients discharged from the geographic area of
interest. For example, if you are using data from the state of Wisconsin
and are interested in generating a rate for Wisconsin, you should remove
the cases where the patient's county of residence (FIPS code) is from
another state. Otherwise the total or overall rate will include the
population of the counties outside Wisconsin.*

The software provides the user with the option of producing output by
MSA or by county. When MSA is selected, urban areas are always defined
by MSAs. When county is selected urban areas will be defined by county.
Rural areas are always defined by county.

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*In the software programs, the MSALEVL parameter indicates whether MSA
codes should be created from the FIPS state/county codes in the input
dataset. If the user wishes to analyze data at the MSA level, this
parameter should be set to "Yes". If the user wishes to analyze data at
the county level, this parameter should be set to "No".*

## Coding of Diagnoses, Procedures, DRGs and MDCs

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*Diagnoses and procedures must be coded using the International
Classification of Diseases, 9th Revision, Clinical Modification
(ICD-9-CM)*

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*Significant modifications to ICD-9-CM codes occurred in the early
1990s. PSI definitions only reflect codes valid after October 1, 1997,
and therefore may not accurately analyze data collected before 1997.*

-   Diagnoses and procedure codes should be in character strings.

-   Diagnosis and procedure codes should not contain any decimal points.

-   Diagnosis and procedure codes should be left justified. Diagnosis
    codes with fewer than five digits should be padded with spaces (not
    zeros) on the right. Procedure codes with fewer than four digits
    should be padded with spaces (not zeros) on the right.

```{=html}
<!-- -->
```
-   *The PSI programs assume accurate and specific coding of ICD codes.
    If an ICD code is specified using 5 digits, the software recognizes
    only 5-digit versions of that code and not truncated versions at 3
    or 4 digits. Similarly, if an ICD code is specified using 4 digits,
    the software recognizes only 4-digit versions of that code and not
    truncated versions at 3 digits. For example, 4281 is the ICD-9-CM
    diagnosis code for left heart failure. If your data are coded less
    specifically (i.e., 428 is used to designate \"heart failure\"),
    these less specific codes are not recognized by the software and
    will result in undercounting cases.*

```{=html}
<!-- -->
```
-   Diagnosis-Related Groups (DRGs) and Major Diagnostic Categories
    (MDCs) are those derived from the Centers for Medicare & Medicaid
    Services (previously Health Care Financing Administration) Medicare
    grouper. The software expects that you will be using the DRG
    effective on the discharge date. The software now refers to data
    elements DRG and MDC. Your data should be coded accordingly.

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*Version 2.1, Revision 2 of the software accounts for ICD-9-CM. DRG and
MDC coding effective through FY 2004 (or through September 30, 2004).*

## Use of External Cause of Injury Codes

External cause of injury codes - E-codes -- are used to classify
environmental events, circumstances, and conditions as the cause of
injury, poisoning, or other adverse events. The use of E-codes is not
always required by a state uniform billing committee or a state data
organization. Users should be knowledgeable of the E-code requirements
and practices of hospitals represented in the input data file. Several
of the indicators use E-codes in their numerator or denominator
definitions. See the "*Guide to the Patient Safety Indicators"*
(<http://www.qualityindicators.ahrq.gov/psi_download.htm>) for
additional information*.*

[]{#__RefHeading___Toc85945152 .anchor}Table 4. Data Elements and Coding
Conventions

+--------+--------------+--------+---------------+--------------------+
| **Va   | **D          | **Fo   | **Value       | **Comments**       |
| riable | escription** | rmat** | description** |                    |
| name** |              |        |               |                    |
+========+==============+========+===============+====================+
| KEY    | Sequence     | N      | User defined  | Not used by the QI |
|        | Number.      | umeric | unique        | programs, but      |
|        | Unique case  |        | numeric       | should be present  |
|        | identifier.  |        | identifier    | to facilitate data |
|        |              |        | for each      | exploration;       |
|        |              |        | discharge     | allows user to     |
|        |              |        | record        | link the records   |
|        |              |        |               | from the           |
|        |              |        |               | PSSAS1.SAS program |
|        |              |        |               | output file back   |
|        |              |        |               | to the original    |
|        |              |        |               | input data file.   |
+--------+--------------+--------+---------------+--------------------+
| AGE    | Age in Years | N      | Age in years  | If this data       |
|        | at Admission | umeric |               | element is missing |
|        |              |        |               | the discharge      |
|        |              |        |               | record will be     |
|        |              |        |               | excluded from the  |
|        |              |        |               | analysis.          |
+--------+--------------+--------+---------------+--------------------+
| AGEDAY | Age in Days  | N      | Age in days   | Not used in the    |
|        | (coded only  | umeric |               | PSI program. If    |
|        | when the age |        |               | not present in the |
|        | in years is  |        |               | input data file it |
|        | less than 1) |        |               | is not necessary   |
|        |              |        |               | to create a dummy  |
|        |              |        |               | variable.          |
+--------+--------------+--------+---------------+--------------------+
| RACE   | Race of      | N      | White         | The values 1, 2,   |
|        | Patient.     | umeric |               | and 3 are used in  |
|        |              |        | Black         | the QI software    |
|        |              | 1      |               | for stratification |
|        |              |        | Hispanic      | (if selected by    |
|        |              | 2      |               | user). All other   |
|        |              |        | Asian or      | ethnicity codes    |
|        |              | 3      | Pacific       | are mapped to an   |
|        |              |        | Island        | 'other' category.  |
|        |              | 4      |               |                    |
|        |              |        | Native        |                    |
|        |              | 5      | American      |                    |
|        |              |        |               |                    |
|        |              | 6      | Other         |                    |
+--------+--------------+--------+---------------+--------------------+
| SEX    | Sex of       | N      | Male          | If this data       |
|        | Patient      | umeric |               | element is missing |
|        |              |        | Female        | the discharge      |
|        |              | 1      |               | record will be     |
|        |              |        |               | excluded from the  |
|        |              | 2      |               | analysis.          |
+--------+--------------+--------+---------------+--------------------+
| PAY1   | Expected     | N      | Medicare      | The values 1, 2,   |
|        | Primary      | umeric |               | 3, and 4 are used  |
|        | Payer        |        | Medicaid      | in the QI software |
|        |              | 1      |               | for stratification |
|        |              |        | Private,      | of the             |
|        |              | 2      | incl. HMO     | Provider-level     |
|        |              |        |               | PSIs (if selected  |
|        |              | 3      | Self-pay      | by user). All      |
|        |              |        |               | other payer codes  |
|        |              | 4      | No charge     | are mapped to an   |
|        |              |        |               | 'other' category.  |
|        |              | 5      | Other         |                    |
|        |              |        |               | This data element  |
|        |              | 6      |               | is used to         |
|        |              |        |               | stratify only the  |
|        |              |        |               | Provider-level     |
|        |              |        |               | PSIs (PSI01-PSI20, |
|        |              |        |               | PSI27-PSI29).      |
+--------+--------------+--------+---------------+--------------------+
| HO     | Location of  | N      | Modified      | Available at:      |
| SPSTCO | Patient      | umeric | Federal       | <http://www.censu  |
|        | Residence or |        | Information   | s.gov/popest/geogr |
|        | Provider     | ssccc  | Processing    | aphic/codes02.pdf> |
|        | Location     |        | Standards     |                    |
|        | (FIPS        |        | State/county  | If this data       |
|        | State/county |        | code[^4]      | element is missing |
|        | code)        |        |               | the discharge      |
|        |              |        |               | record will be     |
|        |              |        |               | excluded from rate |
|        |              |        |               | calculations.      |
+--------+--------------+--------+---------------+--------------------+
| HOSPID | Data Source  | N      | Provider      | Used to facilitate |
|        | Provider     | umeric | i             | data exploration   |
|        | Number       |        | dentification | and possible       |
|        |              |        | number        | trouble shooting.  |
|        |              |        |               | May also be        |
|        |              |        |               | selected as a      |
|        |              |        |               | stratifier (see    |
|        |              |        |               | Table 6).          |
+--------+--------------+--------+---------------+--------------------+
| DISP   | Disposition  | N      | Routine       | The values 2 and   |
|        | of Patient   | umeric |               | 20 are referenced  |
|        |              |        | Short-term    | by the QI code (to |
|        |              | 1      | hospital      | identify transfers |
|        |              |        |               | to another         |
|        |              | 2      | Skilled       | short-term         |
|        |              |        | nursing       | hospital and       |
|        |              | 3      | facility      | patients who died  |
|        |              |        |               | in the hospital).  |
|        |              | 4      | Intermediate  |                    |
|        |              |        | care          |                    |
|        |              | 5      |               |                    |
|        |              |        | Another type  |                    |
|        |              | 6      | of facility   |                    |
|        |              |        |               |                    |
|        |              | 7      | Home health   |                    |
|        |              |        | care          |                    |
|        |              | 20     |               |                    |
|        |              |        | Against       |                    |
|        |              |        | medical       |                    |
|        |              |        | advice        |                    |
|        |              |        |               |                    |
|        |              |        | Died in the   |                    |
|        |              |        | hospital      |                    |
+--------+--------------+--------+---------------+--------------------+
| ATYPE  | Admission    | N      | Emergency     | The values 3 and 4 |
|        | Type         | umeric |               | are referenced by  |
|        |              |        | Urgent        | the PSI code (to   |
|        |              | 1      |               | identify elective  |
|        |              |        | Elective      | surgeries and      |
|        |              | 2      |               | newborn            |
|        |              |        | Newborn       | admissions). PSIs  |
|        |              | 3      |               | 10, 11, 13, and 17 |
|        |              |        | Delivery      | will be affected   |
|        |              | 4      |               | if ATYPE values    |
|        |              |        | Other         | are missing.       |
|        |              | 5      |               |                    |
|        |              |        |               |                    |
|        |              | 6      |               |                    |
+--------+--------------+--------+---------------+--------------------+
| A      | Admission    | N      | ER            | The values 2 and 3 |
| SOURCE | Source       | umeric |               | are referenced by  |
|        |              |        | Another       | the PSI code (to   |
|        |              | 1      | hospital      | identify transfers |
|        |              |        |               | from another       |
|        |              | 2      | Another       | hospital or        |
|        |              |        | facility incl | facility)          |
|        |              | 3      | LTC           |                    |
|        |              |        |               |                    |
|        |              | 4      | Court/law     |                    |
|        |              |        | enforcement   |                    |
|        |              | 5      |               |                    |
|        |              |        | Routin        |                    |
|        |              |        | e/birth/other |                    |
+--------+--------------+--------+---------------+--------------------+
| LOS    | Length of    | N      | Number of     |                    |
|        | Stay         | umeric | days from     |                    |
|        |              |        | admission to  |                    |
|        |              |        | discharge     |                    |
+--------+--------------+--------+---------------+--------------------+
| A      | APR_DRG      | N      | APR-DRG from  | Not used by the    |
| PR_DRG | Category     | umeric | 3M software   | PSI program. If    |
|        |              |        |               | not present in the |
|        |              |        |               | input data file it |
|        |              |        |               | is not necessary   |
|        |              |        |               | to create a dummy  |
|        |              |        |               | variable.          |
+--------+--------------+--------+---------------+--------------------+
| S      | APR_DRG      | N      | APR-DRG       | Not used by the    |
| EVERTY | Severity     | umeric | Severity      | PSI program. If    |
|        | Score        |        | Score from 3M | not present in the |
|        |              |        | software      | input data file it |
|        |              |        |               | is not necessary   |
|        |              |        |               | to create a dummy  |
|        |              |        |               | variable.          |
+--------+--------------+--------+---------------+--------------------+
| RI     | APR_DRG      | N      | APR-DRG Risk  | Not used by the    |
| SKMORT | Mortality    | umeric | of Mortality  | PSI program. If    |
|        | Score        |        | Score from 3M | not present in the |
|        |              |        | software      | input data file it |
|        |              |        |               | is not necessary   |
|        |              |        |               | to create a dummy  |
|        |              |        |               | variable.          |
+--------+--------------+--------+---------------+--------------------+
| DRG    | Diagnosis    | N      | DRG from      |                    |
|        | Related      | umeric | federal (CMS) |                    |
|        | Group        |        | Grouper       |                    |
+--------+--------------+--------+---------------+--------------------+
| MDC    | Major        | N      | MDC from      |                    |
|        | Diagnostic   | umeric | federal (CMS) |                    |
|        | Category     |        | grouper       |                    |
+--------+--------------+--------+---------------+--------------------+
| DX1 -- | ICD-9-CM     | S      | Diagnosis     | Users must specify |
| DX30   | Diagnosis    | tring, | codes         | the number of      |
|        | Codes. DX1   | 5      |               | diagnosis          |
|        | is the       | cha    |               | variables as a     |
|        | principal    | racter |               | parameter in the   |
|        | diagnosis,   |        |               | PSSPS1.SPS program |
|        | DX2-DX30 are |        |               | (!maxdx).          |
|        | secondary    |        |               |                    |
|        | diagnoses.   |        |               |                    |
|        |              |        |               |                    |
|        | **Note**: If |        |               |                    |
|        | e-codes are  |        |               |                    |
|        | separated    |        |               |                    |
|        | from         |        |               |                    |
|        | secondary    |        |               |                    |
|        | diagnoses in |        |               |                    |
|        | the input    |        |               |                    |
|        | data file,   |        |               |                    |
|        | the variable |        |               |                    |
|        | should be    |        |               |                    |
|        | renamed and  |        |               |                    |
|        | included as  |        |               |                    |
|        | a secondary  |        |               |                    |
|        | diagnosis    |        |               |                    |
|        | variable     |        |               |                    |
|        | (e.g.,       |        |               |                    |
|        | e-codes      |        |               |                    |
|        | would be     |        |               |                    |
|        | labeled as   |        |               |                    |
|        | DX10 in a    |        |               |                    |
|        | data file    |        |               |                    |
|        | where the    |        |               |                    |
|        | last         |        |               |                    |
|        | secondary DX |        |               |                    |
|        | field is     |        |               |                    |
|        | DX9).        |        |               |                    |
+--------+--------------+--------+---------------+--------------------+
| NDX    | Count of the | N      | Count of      | If not present in  |
|        | Number of    | umeric | diagnoses     | the input data     |
|        | Diagnoses    |        |               | file it is         |
|        | (DX) on the  |        | (principal    | necessary to       |
|        | Discharge    |        | and all       | create it.         |
|        | Record.      |        | secondary     | Definition is: if  |
|        |              |        | diagnoses)    | the 1st discharge  |
|        |              |        |               | record has 5 DX    |
|        |              |        |               | and the 2nd has    |
|        |              |        |               | 10, NDX would be 5 |
|        |              |        |               | on the 1^st^ and   |
|        |              |        |               | 10 on the 2^nd^.   |
+--------+--------------+--------+---------------+--------------------+
| PR1 -- | Procedure    | S      | Procedure     | Users must specify |
| PR30   | ICD-9-CM     | tring, | codes         | the number of      |
|        | Codes. PR1   | 4      |               | procedure          |
|        | is the       | cha    |               | variables as a     |
|        | principal    | racter |               | parameter in the   |
|        | procedure,   |        |               | PSSPS1.SPS program |
|        | PR2-PR30 are |        |               | (!maxpr).          |
|        | secondary    |        |               |                    |
|        | procedures.  |        |               |                    |
+--------+--------------+--------+---------------+--------------------+
| NPR    | Count of the | N      | Count of      | If not present in  |
|        | Number of    | umeric | procedures    | the input data     |
|        | Procedures   |        |               | file it is         |
|        | (PR) on the  |        | (principal    | necessary to       |
|        | Discharge    |        | and all       | create it.         |
|        | Record.      |        | secondary     | Definition is: If  |
|        |              |        | procedures)   | the 1^st^          |
|        |              |        |               | discharge record   |
|        |              |        |               | has 1 PR and the   |
|        |              |        |               | 2^nd^ has 2, NPR   |
|        |              |        |               | would be 1 for the |
|        |              |        |               | 1^st^ record and 2 |
|        |              |        |               | for the 2^nd^.     |
|        |              |        |               |                    |
|        |              |        |               | Not used by the    |
|        |              |        |               | SPSS program.      |
+--------+--------------+--------+---------------+--------------------+
| PRDAY1 | Days from    | N      | Days from     | Necessary          |
| --     | Admission to | umeric | admission to  | variables if the   |
| P      | Procedure.   |        | procedure[^5] | user sets the      |
| RDAY30 | PR1 is the   |        |               | &PRDAY parameter   |
|        | principal    |        |               | in PSSPS1.SPS to   |
|        | procedure,   |        |               | equal one. In this |
|        | PR2-PR30 are |        |               | case, it is        |
|        | secondary    |        |               | expected that the  |
|        | procedures.  |        |               | number of PRDAY    |
|        |              |        |               | variables agrees   |
|        |              |        |               | with the number of |
|        |              |        |               | Procedure codes    |
|        |              |        |               | present. .         |
|        |              |        |               |                    |
|        |              |        |               | These variables    |
|        |              |        |               | are not needed if  |
|        |              |        |               | the user sets the  |
|        |              |        |               | &PRDAY parameter   |
|        |              |        |               | in PSSPS1.SPS to   |
|        |              |        |               | equal zero,        |
|        |              |        |               | indicating that    |
|        |              |        |               | there is no        |
|        |              |        |               | procedure day      |
|        |              |        |               | information        |
|        |              |        |               | available.         |
+--------+--------------+--------+---------------+--------------------+

## Missing Values

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*The PSI programs do not distinguish among different types of missing
values.*

Data files of hospital discharge abstract data may have numeric data
elements coded using SPSS system missing \"dot\" values. For example,
besides the standard SPSS value of "." for missing data, there might
also be present values of "-1" for invalid data, "-2" for data
unavailable from a particular source, and "-3" for inconsistent data.
However, the PSI programs do **not** distinguish among the different
types of missing codes. Therefore, all types of missing values in the
input data to the PSI module can be represented by a single value -
missing data (.) for numeric variables and blank (\' \') for
alphanumeric (or character) variables.

## Treatment of Missing Data

The software is designed to handle missing data in a particular manner;
specifically the software requires confirmation for the assignment of a
poor outcome or negative event. For instance, in order to be assigned as
a death, each case must actually be coded as a death. Missing data is
considered neutral. Missing data for some elements results in the
exclusion of that case from the denominator. For a few other elements,
the case is retained. Table 5 lists the impact of missing data for each
data element.

[]{#__RefHeading___Toc85945153 .anchor}Table 5. Treatment of Missing
Data Elements

  ----------------------------------------------------------------------------------------------------
  **Variable**     **Label**            **D**   **N**   **E**   **S**   **Treatment of Missing Data**
  ---------------- -------------------- ------- ------- ------- ------- ------------------------------
  AGE              Age In Years At      X       X       X       X       Case excluded from all
                   Admission                                            analysis (e.g., dropped from
                                                                        the denominator of the
                                                                        discharge based indicators and
                                                                        from numerator of all
                                                                        population based measures).

  ASOURCE          Admission Source                     X               Case excluded from denominator
                                                                        where used in specification
                                                                        (e.g., PSI 3).

  ATYPE            Admission Type       X                               Case excluded from denominator
                                                                        where used in specification
                                                                        (e.g., PSI 10).

  DISP             Disposition Status           X       X               Case excluded from denominator
                                                                        where used in specification
                                                                        (e.g., PSI 4).

  DRG              Diagnosis Related    X       X       X               Case excluded from denominator
                   Group (CMS DRG) in                                   (e.g., PSI 1) and from
                   Effect on Discharge                                  numerator (e.g., PSI 21) where
                   Date                                                 used in specification.

  LOS              Length of Stay       X               X               Case excluded from denominator
                                                                        where used in specification
                                                                        (e.g., PSI 3).

  SEX              Patient Gender       X       X               X       Case excluded from all
                                                                        analysis (e.g., dropped from
                                                                        the denominator of the
                                                                        discharge based indicators and
                                                                        from numerator of all
                                                                        population based measures).

  HOSPSTCO         Location of Patient  X                               Dropped from denominator in
                   Residence or                                         rate calculations (stratified
                   Hospital Location                                    by county or MSA), case will
                   Modified FIPS                                        appear in calculation of the
                   State/County Code                                    overall rate.

  MDC              Major Diagnostic     X               X               Case excluded from denominator
                   Category (CMS MDC)                                   (e.g., PSI 3) and from
                   In Effect On                                         numerator (e.g., PSI 22) where
                   Discharge Date                                       used in specification.

  RACE             Race                                         X       Classified As "Other."

  D --                                                                  
  Denominator; N                                                        
  -- Numerator; E                                                       
  -- Exclusion; S                                                       
  --                                                                    
  Stratification                                                        
  ----------------------------------------------------------------------------------------------------

# User Options

The PSI software reflects the development and implementation of the
software with discharge data available to AHRQ through the HCUP program.
Our goal was to develop the tools, illustrate their use, and then
encourage others to adopt and use the tools for their own applications.
As a result, users are encouraged to consider how AHRQ may modify the
PSI software to better serve their measurement needs and interests.

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*Modifications to the definitions of outcomes of interest (numerators)
or populations at risk (denominators) are possible but not desirable.
Maintaining consistent definitions is important. Once definitions are
altered, the ability to make comparisons of PSIs based on original
definitions is lost. Users are encouraged to identify ways to improve
the PSI methodology and to share their suggestions with AHRQ for future
updates.*

AHRQ provides public access to HCUPnet - an interactive tool for
identifying, tracking, analyzing, and comparing statistics on hospital
care. HCUPnet queries generate statistics in a table format using data
from the Nationwide Inpatient Sample (NIS) and State Inpatient Databases
(SID) for those States that have agreed to participate. HCUPnet includes
statistics based on the AHRQ Quality Indicators (QIs) which have been
applied to the HCUP NIS. If users change definitions of the PSIs, it
will not be possible to compare users' results to the national estimates
in HCUPnet. HCUPnet may be accessed through the HCUP web site at
<http://hcup.ahrq.gov/HCUPnet.asp>.

# Producing Patient Safety Indicator Rates: Processing Steps 

Each Patient Safety Indicator (PSI) expressed as a rate, is simply
defined as:

Outcome of interest / Population at risk

(or)

Numerator / Denominator

Conceptually, five steps are necessary to produce the PSI rates. The
following describes the steps and how the software performs them.

## 1. Identify outcomes in inpatient records

> Inpatient records are marked to indicate whether they contain the
> outcome of interest (numerator or "top") for each of the AHRQ PSI
> measures.
>
> This is done by setting a series of flag variables, each of which
> corresponds to the numerator for a particular PSI. For example, if the
> inpatient record meets the conditions for inclusion in the outcome for
> PSI #1, then the outcome indicator for PSI #1 is set to 1.
>
> This step requires one pass through the discharge-level data and
> outputs a discharge-level data file containing the flag indicator
> variables for the outcomes for each PSI. This output file also
> contains the original input variables, with the exception of the
> diagnosis and procedure variables which have been removed to reduce
> the size of the output file.

## 2. Identify populations at risk

> For the Provider PSIs, the populations at risk (the denominators for
> calculating the PSI rates, or "pop") are derived from the hospital
> discharge records.
>
> For the Area PSIs, the populations at risk (the denominators for
> calculating the PSI rates) are derived from Census population figures.

## 3. Calculate observed (raw) Patient Safety Indicator rates

> Using the output data from step 1 and either hospital discharge or
> Census population data from step 2, the PSI rates are calculated for
> user-specified combinations of stratifiers. These stratifiers include
> hospitals, age groups, race/ethnicity categories, sex, and payer
> categories for the Provider PSIs, and areas (MSAs/counties), age
> groups, race/ethnicity categories, and sex for the Area PSIs.

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*The programs calculate observed PSI rates regardless of the number of
cases available. However, PSI rates based on only a few cases should be
interpreted with caution.*

> In performance measurement work, it is recommended that rates be
> suppressed when there are fewer than 30 cases in the numerator or the
> denominator. This exclusion rule serves two purposes:

-   It eliminates unstable estimates based on too few cases.

-   It helps protect the identities of hospitals and patients.

> This step outputs the observed rates for user-specified categories,
> alone or in combination. For example, Provider PSI observed rates
> could be output at the hospital level, at the payer level, or at the
> hospital level by payer.

## 4. Risk-adjust the Patient Safety Indicator Rates. Provider PSIs only.

> Overall file means and regression coefficients from a baseline
> database (reflecting a large proportion of the U.S. population) are
> applied to the observed rates in the risk-adjustment process. These
> baseline file means and regression coefficients are provided as part
> of the PSI module. The risk-adjusted rates will then reflect the age,
> sex, modified DRG, and comorbidity distribution of data in the
> baseline file rather than the distribution for the hospitals present
> in the users' data. This will allow risk-adjusted rates produced by
> various users to be compared directly to one another. The overall
> means and regression coefficients were derived from the HCUP Year 2000
> State Inpatient Data (SID) for 27 states. The code to generate these
> baseline means and coefficients are not part of the PSI module.
>
> ![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
> *For the Provider Indicators, if there are fewer than three discharges
> for the particular PSI for a particular combination of stratifiers,
> then the risk-adjusted rate for that combination of stratifiers is set
> to missing.*

## 5. Create MSX Smoothed Rates. Provider PSIs Only

> Shrinkage factors are applied to the risk-adjusted rates for each PSI
> in a process called multivariate signal extraction (MSX). These
> shrinkage factors were calculated from the HCUP Year 2000 SID of 27
> states. For each PSI, the shrinkage estimate reflects a 'reliability
> adjustment' unique to each indicator. The less reliable the PSI over
> time and across hospitals, the more the estimate 'shrinks' the PSI
> toward the overall mean. The resulting rate will appear "smoother"
> than the raw rate, meaning the year-to-year fluctuations in
> performance are likely to be reduced. More information on interpreting
> smoothed rates is contained in the interpretation section of this
> document. The shrinkage factors are provided as part of the PSI
> software and do not need to be calculated by users.

These five steps reflect the PSI module production in a nutshell. The
next section of this document describes the specifics of each software
component of the PSI module software.

# Program Descriptions

This section describes the four SPSS programs that assign, calculate,
and print the Patient Safety Indicators.

For each program there is a description, a list of input and output
files, and an explanation of changes to the program that may be
required. The flow of data through the PSI module programs is shown in
the flowcharts in Figure 1 and Figure 2 that begin on page
[3](#__RefHeading___Toc85945147).

If you desire to create and examine observed PSI rates, then the PSSPS1
programs will need to be used, followed by PSSPSP2 (for Provider
observed rates) and/or PSSPSA2 (for Area observed rates). If you also
wish to create Provider risk-adjusted and smoothed PSI rates, then you
will also need to run the PSSPSP3 program. Risk-adjusted and smoothed
rates are not calculated for the Area PSIs.

## Program 1: Run PSSPS1

The PSSPS1 program processes hospital discharge abstract data, sets
comorbidity indicators, and flags inpatient records if they contain
outcomes of interest. Outcome indicator names have prefix of "T"
([T]{.underline}op). Stratifier variables are constructed at the
beginning of the program.

This program assumes that the input data file (consisting of inpatient
discharge abstract data) conforms to specific variable names,
attributes, and coding conventions. See Table 4 on page
[11](#__RefHeading___Toc85945152) for variable names and attributes for
the input data file.

Partial definitions of the Patient Safety Indicators are given in Table
1 on page [5](#__RefHeading___Toc85945149). This table is presented to
assist those individuals who desire to examine the software source code
statements. Complete definitions of the indicators are given in Appendix
A of the "*Guide to Patient Safety Indicators".*
(*<http://www.qualityindicators.ahrq.gov/psi_download.htm>).*

The AHRQ Comorbidity Analysis Program (comoanaly.sas), available at
<http://www.hcup-us.ahrq.gov/toolssoftware/comorbidity/comorbidity.jsp>
, has been included as part of program PSSPS1. This code adds the
comorbidity indicators to each discharge record. The user does not need
to access the AHRQ Comorbidity Analysis Program.

[Input]{.underline}:

1.  User supplied SPSS inpatient data set consisting of administrative
    hospital discharge abstract data. This data set is a discharge level
    file with an array of diagnosis and procedure codes, among other
    data elements.

[Output]{.underline}:

1.  SPSS dataset containing inpatient records with input variables,
    stratifiers, comorbidity variables, and flag indicators (TPPSxx and
    TAPSxx) for the outcomes of interest that will later form the
    numerators for the PSI rates.

2.  Descriptives (with N, MIN, MAX, MEAN and SUM) of all of the numeric
    variables in the output data file.

[Changes]{.underline}:

> Change the !LET parameters at the top of the program to specify the
> following:

1.  !INFILE should specify the directory and file name of the input SPSS
    data set containing discharge records with procedures and diagnoses.

2.  !OUTFILE should specify the directory and file name of the output
    SPSS data set containing patient safety and comorbidity indicators.

3.  !PRDAY should specify whether the input SPSS data set contains
    variables indicating the number of days from admission to the
    procedure. If the file contains PRDAY variables then !PRDAY should
    be set to "Yes", otherwise !PRDAY should be set to "No".

4.  !MSALEVL is a flag to indicate whether MSAs should be constructed
    from the county identifiers on the input dataset. Users who wish to
    calculate rates at the MSA level rather than the county level should
    set this flag to "Yes"; otherwise they should set this flag to "No".
    The MSA identifier is saved as a separate variable from the county
    identifier variable, so users who create MSAs will still have the
    opportunity to construct county and/or MSA level area rates.

5.  !LASTDX should specify the number of diagnosis variables on the
    file. By default this value is set to 30.

> ![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
> *Users with fewer or more diagnosis codes should modify this value
> accordingly.*

6.  !LASTPR should specify the number of procedure variables on the
    file. By default this value is set to 30.

> ![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
> *Users with fewer or more procedure codes should modify this value
> accordingly.*
>
> ![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
> *If your variables are named differently from those used in the PSI
> software (see Table 4 on page [11](#__RefHeading___Toc85945152)), you
> MUST either rename those variables prior to running this program or
> modify PSSPS1 to include the renaming of your variables to match those
> expected by the software. Similarly, if your variables are not the
> same type, i.e., character or numeric, as those expected by the
> software (see Table 4), you MUST modify your variables prior to
> running this program.*

## Program 2: Run PSSPSP2 

The PSSPSP2 program calculates the observed or raw rates for the
Provider-level Patient Safety Indicators, using the data derived in a
previous step (PSSPS1). These observed rates are stratified by
combinations of providers, sex, age, race, and payer categories. The
program first totals the indicator flags created by the PSSPS1 program
and then for each of the desired stratifiers divides these totals by the
hospital discharges in the universe for the indicator. The population
denominators are stored in variables with names that have a prefix of
"P" ([P]{.underline}op). The [O]{.underline}bserved rates are stored in
variables that have a prefix of "O".

[Input]{.underline}:

1.  The SPSS dataset that was created in the PSSPS1. This is a
    discharge-level file that contains inpatient records with input
    variables, stratifiers, and the 23 new flag indicators for the PSI
    Provider outcomes of interest.

[Output]{.underline}:

1.  SPSS dataset with summary records that contain observed rates
    (OPPSxx variables where xx refers to the indicator number), the
    counts of outcomes that formed the numerators of the rates (TPPSxx
    variables), and the hospital discharge totals that formed the
    denominators of the observed rates (PPPSxx variables). The output
    file has records summarized to the various combinations of
    stratifiers specified in the !STRLEVS parameter that is described in
    item 5 in "Changes" below.

2.  Descriptive statistics (with N, NMISS, MIN, MAX, MEAN, and SUM) of
    the provider-level summary records that shows statistics for the
    OPPSxx observed rates, the TPPSxx counts of outcomes that formed the
    numerators of the rates, and the PPPSxx counts of outcomes that
    formed the denominators of the rates. These means will only be
    generated if the user included a value of 16 for the !STRLEVS
    parameter discussed in item 5 in the "[Changes]{.underline}" section
    below.

3.  An optional listing of the output summary dataset is provided at the
    end of the hardcopy printout. This printout may be quite large
    depending on the number and the types of stratifications that the
    user requests with the !STRLEVS parameter discussed in item 5 in the
    "[Changes]{.underline}" section below. If the user does not wish to
    generate this printout, then the !PRINT parameter should be set to
    "No".

[Changes]{.underline}:

> Change the !LET parameters at the top of the program to specify the
> following:

1.  !TEMPDIR should specify the name of an existing directory where SPSS
    can store temporary files. These files should be deleted once the
    program completes.

> ![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
> *A pathname must end with the character \"\\\" as shown in the example
> below:*
>
> !let !tempdir = \'c:\\PSI\\\'

2.  !PERMDIR should specify the name of an existing directory where SPSS
    can store permanent files, including the name of the data set
    created by program 1.

3.  !INDATA should specify the name of the SPSS dataset created by
    program 1 containing the comorbidity and patient safety indicator
    flags.

4.  !OUTDAT should specify the name of the final SPSS data set that will
    be created by this program that will contain the provider observed
    rates.

5.  !STRLEVS should specify the levels of stratification for which the
    program should calculate observed rates. The levels should be
    specified as a list of numbers (1 to 31 separated by commas)
    corresponding to the following stratifications shown in Table 6.

[]{#__RefHeading___Toc85945154 .anchor}Table 6. PSSPSP2 Aggregation
Possibilities

  --------------------------------------------------------------------------------------
  **STRAT**        **Stratification**                                           
  ---------------- -------------------- -- ------- --- ------ --- --------- --- --------
  1                                                                             Race

  2                                                               Payer         

  3                                                               Payer         Race

  4                                                    Sex                      

  5                                                    Sex                      Race

  6                                                    Sex        Payer         

  7                                                    Sex        Payer         Race

  8                                        Age                                  

  9                                        Age                                  Race

  10                                       Age                    Payer         

  11                                       Age                    Payer         Race

  12                                       Age         Sex                      

  13                                       Age         Sex                      Race

  14                                       Age         Sex        Payer         

  15                                       Age         Sex        Payer         Race

  **16**           **Provider**                                                 

  17               Provider                                                     Race

  18               Provider                                       Payer         

  19               Provider                                       Payer         Race

  20               Provider                            Sex                      

  21               Provider                            Sex                      Race

  22               Provider                            Sex        Payer         

  23               Provider                            Sex        Payer         Race

  24               Provider                Age                                  

  25               Provider                Age                                  Race

  26               Provider                Age                    Payer         

  27               Provider                Age                    Payer         Race

  28               Provider                Age         Sex                      

  29               Provider                Age         Sex                      Race

  30               Provider                Age         Sex        Payer         

  31               Provider                Age         Sex        Payer         Race
  --------------------------------------------------------------------------------------

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
STRAT=0 (Overall) is calculated automatically. STRAT=16 (Provider) is
the default.

> For example, if you are using a state inpatient hospital database, you
> might specify the following STRAT values to the !STRLEVS parameter:
>
> 0 -- provides overall rates for your entire state
>
> 8 -- provides overall rates for your state, broken down by age groups
>
> 16 -- provides rates for providers within your state
>
> 24 -- provides rates for age groups within these providers

6.  The !PRINT parameter should indicate whether the final dataset
    should be listed or not. If !PRINT is set to \"Yes\", then the
    program will generate a listing for each of the 23 Provider
    Indicators, including the numerator, denominator and observed rate
    for each level of stratification specified by the !STRLEVS
    parameter. If the user does not want to generate this listing, the
    !PRINT parameter should be set to \"No\".

## Program 3: Run PSSPSP3

The PSSPSP3 program calculates age, sex, modified DRG and comorbidity
risk-adjusted rates for each PSI and then calculates smoothed rates.

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*If you are interested in calculating confidence intervals for each PSI,
you may request a supplementary module (PSSPSP3CI.SPS) to calculate a
95% CI for each PSI and provider (see the Interpreting the Results,
Confidence Intervals section for additional information). You would run
this program in place of PSSPSP3. The user needs to run only PSSPSP3 or
PSSPSP3CI, it is not necessary to run both these programs.*

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*When there are fewer than three discharges within a stratification
cell, the risk-adjusted rates are set to missing. The smoothed rates
that are based on these risk-adjusted rates are also set to missing.*

The output file has records summarized to the various combinations of
stratifiers that were specified in the !STRLEVS parameter of the
preceding QISPSP2 program. See Table 6 on page
[21](#__RefHeading___Toc85945154).

[Input]{.underline}:

1.  The discharge-level SPSS data set that was created with the PSSPS1
    program.

2.  The SPSS data set with summary records that was created with the
    PSSPSP2 program.

3.  The AHRQ-supplied text file (COVPSP00.TXT) containing regression
    coefficients from a regression that was run on a reference SID
    dataset. These coefficients will be used in the risk adjustment
    process. This file is provided to you as part of the PSI module. The
    text file does not need to be converted to a SPSS file for use with
    the software.

4.  The AHRQ-supplied text file (MSXPSP_0.TXT) containing three arrays
    for use in the smoothing process. The arrays contain noise
    estimates, signal estimates, and mean rates for each PSI. This file
    is provided to you as part of the PSI module. The text file does not
    need to be converted to a SPSS file for use with the software.

[Output]{.underline}:

1.  A SPSS dataset with an overall summary record and with
    provider-level summary records that contain the three types of
    indicator rates, along with the components of the initial raw rates.
    Specifically, the file contains the observed rates (OPPSxx
    variables), the risk-adjusted rates (RPPSxx variables), the smoothed
    rates (SPPSxx variables), the counts of outcomes that formed the
    numerators of the observed rates (TPPSxx variables), and the
    hospital discharge totals that formed the denominators of the
    observed rates (PPPSxx variables).

2.  Descriptive statistics (with N, NMISS, MIN, MAX, MEAN, and SUM) of
    the provider-level summary records that shows statistics for the
    observed, risk-adjusted and smoothed rates, and statistics for the
    counts of outcomes that formed the numerators and denominators of
    the observed rates. These means will only be generated if the user
    included a value of 16 for the !STRLEV parameter of the preceding
    QISPSP2 program. See Table 6 on page
    [21](#__RefHeading___Toc85945154).

3.  An optional listing of the output summary dataset is provided at the
    end of the hardcopy printout. This printout may be quite large
    depending on the number and the types of stratifications that the
    user requested with the !STRLEVS parameter of the preceding PSSPSP2
    program. See Table 6 on page [21](#__RefHeading___Toc85945154). If
    the user does not wish to generate this printout, then the !PRINT
    parameter should be set to "No".

[Changes]{.underline}:

> Change the !LET parameters at the top of the program to specify the
> following:

1.  !PERMDIR should specify the name of an existing directory where SPSS
    can store permanent files. This directory should include the final
    output data sets created by programs PSSPS1 and PSSPS2P.

2.  !TEMPDIR should specify the name of an existing directory where SPSS
    can store temporary files. These files should be deleted once the
    program completes.

3.  !TEXTDIR should specify the name of the existing directory where
    AHRQ-supplied text files were saved. The files in this directory
    should not be converted to SPSS format.

4.  !COVARA should specify the name of the AHRQ-supplied text file
    (contained within the !TEXTDIR directory) where regression
    coefficients needed to risk adjust the indicators are located.

5.  !MSXFILE should specify the name of the AHRQ-supplied text file
    (contained within the !TEXTDIR directory) containing arrays of
    coefficients used to smooth the risk adjusted rates.

6.  !STRLEVS should specify the stratification levels. This should be
    consistent with program PSSPSP2.

7.  !PRDAY is a flag to indicate whether the user-supplied inpatient
    discharge records contain fields for number of days from admission
    to the procedure. If the input file contains PRDAY variables, this
    flag should be set to "Yes", otherwise it should be set to "No".

```{=html}
<!-- -->
```
7.  The !PRINT parameter should indicate whether the final dataset
    should be listed or not. If !PRINT is set to \"Yes\", then the
    program will generate a listing for each of the 23 Provider
    Indicators, including the numerator, denominator and observed rate
    for each level of stratification specified by the !STRLEVS
    parameter. If the user does not want to generate this listing, the
    !PRINT parameter should be set to \"No\".

## Program 4: Run PSSPSA2

The PSSPSA2 program calculates the observed or raw rates for the
area-level Patient Safety Indicators, using the data derived from
Program 1 (PSSPS1). These observed rates are stratified by combinations
of area, sex, age, and race categories. The program first totals the six
area indicator flags created by the PSSPS1 program, and then for each of
the desired stratifiers divides these totals by the pertinent
residential population. The population denominators are stored in
variables with names that have a prefix of "P" ([P]{.underline}op). The
[O]{.underline}bserved rates are stored in variables that have a prefix
of "O".

[Input]{.underline}:

1.  The SPSS dataset that was created in the PSSPS1. This is a
    discharge-level file that contains inpatient records with input
    variables, stratifiers, and the six new flag indicators for the PSI
    Area outcomes of interest.

2.  A text file with Census area residential populations, stratified by
    area, age, sex, and ethnicity categories. Five such files are
    currently provided along with the PSI module software. The files are
    QICTY97, QICTY98, QICTY99, QICTY00, QICTY01 and QICTY02. The user
    should select the file for the year that best matches the user's
    discharge datafile.

> ![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
> *Users do **not** need to convert the ASCII text file to a SPSS
> dataset for use with the software.*

[Output]{.underline}:

1.  SPSS dataset with summary records that contain observed rates
    (OAPSxx variables where xx refers to the indicator number), the
    counts of outcomes that formed the numerators of the rates (TAPSxx
    variables), and the residential population totals that formed the
    denominators of the observed rates (PAPSxx variables). The output
    file has records summarized to the various combinations of
    stratifiers specified in the !STRLEVS parameter that is described in
    item 7 in "Changes" below.

2.  Descriptive statistics (with N, NMISS, MIN, MAX, MEAN, and SUM) of
    the area-level summary records that shows statistics for the OAPSxx
    observed rates, the TAPSxx counts of outcomes that formed the
    numerators of the rates, and the PAPSxx residential populations
    totals. These means will only be generated if the user included a
    value of 8 for the !STRLEVS parameter discussed in item 5 in the
    "[Changes]{.underline}" section below.

3.  An optional listing of the output summary dataset is provided at the
    end of the hardcopy printout. This printout may be quite large
    depending on the number and the types of stratifications that the
    user requests with the !STRLEVS parameter discussed in item 7 in the
    "[Changes]{.underline}" section below. If !PRINT is set to \"Yes\",
    then the program will generate a listing for each of the six Area
    Indicators, including the numerator, denominator and observed rate
    for each level of stratification specified by the !STRLEVS
    parameter. If the user does not want to generate this listing, the
    !PRINT parameter should be set to \"No\".

[Changes]{.underline}:

> Change the !LET parameters at the top of the program to specify the
> following:

1.  !PERMDIR should specify the name of an existing directory where SPSS
    can store permanent files. This directory should include the final
    output data set created by programs PSSPS1.

2.  !TEMPDIR should specify the name of an existing directory where SPSS
    can store temporary files. These files should be deleted once the
    program completes.

3.  !TEXTDIR should specify the name of the existing directory where
    AHRQ-supplied text files were saved. The files in this directory
    should not be converted to SPSS format.

4.  !INDATA should specify the name of the SPSS data set output from
    program 1 that will used as input for calculating the observed
    rates. This data set must be saved in the directory specified by
    !PERMDIR.

5.  !OUTDAT should specify the name of the SPSS data set to be output
    from this program with the observed rates. This data set will be
    saved in the directory specified by !PERMDIR.

6.  !POPFILE should specify the name of the AHRQ-supplied text file
    (located within the !TEXTDIR directory) to be used for constructing
    population denominators used in the area rates.

7.  []{#_Ref83545298 .anchor}!STRLEVS should specify the comma separated
    list of stratification levels for which area rates are to be
    calculated. The stratification levels include the following:

[]{#__RefHeading___Toc85945155 .anchor}Table 7. PSSPSA2 Aggregation
Possibilities

  ------------------- -------------------- ---- ------- --- ------- ---- ------------
  **STRAT**           **Stratification**                                 

  1                                                                      Race

  2                                                         Sex          

  3                                                         Sex          Race

  4                                             Age                      

  5                                             Age                      Race

  6                                             Age         Sex          

  7                                             Age         Sex          Race

  **8**               **Area**                                           

  9                   Area                                               Race

  10                  Area                                  Sex          

  11                  Area                                  Sex          Race

  12                  Area                      Age                      

  13                  Area                      Age                      Race

  14                  Area                      Age         Sex          

  15                  Area                      Age         Sex          Race
  ------------------- -------------------- ---- ------- --- ------- ---- ------------

> ![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
> STRAT=0 (Overall) is calculated automatically; STRAT=8 (area) is the
> default.
>
> For example, if you are using a state inpatient hospital database, you
> might specify the following !STRLEVS values:
>
> 0 -- provides overall rates for your entire state
>
> 4 -- provides overall rates for your state, broken down by age groups
>
> 8 -- provides rates for areas within your state
>
> 12 -- provides rates for age groups within these areas

8.  !MSALEVL is a flag to indicate whether rates in urban areas should
    be calculated at the MSA level rather than at the county level.
    Rural areas are calculated at the county level in either case. To
    calculate urban rates at the MSA level, set this flag to "Yes",
    otherwise set it to "No".

> ![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
> *Additionally, in order to calculate MSA level area rates, the
> !MSALEVL flag on program 1 must also have been set to "Yes".*

9.  The !PRINT parameter should indicate whether the final dataset
    should be listed or not. If !PRINT is set to \"Yes\", then the
    program will generate a listing for each of the six indicators,
    including the numerator, denominator and observed rate for each
    level of stratification specified by the !STRLEVS parameter. If the
    user does not want to generate this listing, the !PRINT parameter
    should be set to \"No\".

# Reviewing the Printed Output

This section contains tips for reviewing some of the printed output from
the PSI module. These tips are oriented toward explaining the
interrelationships between printout items from different programs and
hopefully will help to reveal the nature and structure of the module
outputs. For guidance in interpreting the results, see the next section
which begins on page [Error: Reference source not
found](#interpretation).

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*The final output of the PSI module is a LISTING from PSSPSP3 (for
Provider-level Indicators) and PSSPSA2 (for Area-level Indicators). All
interim printouts are for checking and trouble-shooting. However, if you
have elected to refrain from risk adjusting and smoothing the Provider
Indicators, then the final Provider Indicator output will be the LISTING
at the end of the PSSPSP2 program. Risk-adjusted and smoothed rates are
not calculated for the Area-level PSIs.*

## PSSPS1

The initial printout from the PSSPS1 program contains descriptive
statistics output for all of the numeric variables (including the
comorbidity indicators) in the output discharge-level dataset. It will
contain information for the newly constructed TAPSxx and TPPSxx flag
variables that will later form the numerators for the indicator rates.
For each TAPSxx and TPPSxx flag variable:

-   The SUM will contain the total number of observations in the dataset
    that were found to have the particular outcome of interest.

-   For the six Area Indicators (TAPS21-TAPS26), the MEAN, MINIMUM and
    MAXIMUM will usually be one since the flag variables have either
    been set to missing ('.') or to a value of one. The Provider
    Indicators (TPPS01-TPPS20, TPPS27-TPPS29) will have a value of one,
    zero, or missing ('.'). For these indicators, a value of zero was
    assigned to the TPPSxx flag if a particular observation was part of
    the population at risk for a particular indicator but did not have
    the particular outcome of interest. For example, TPPS20 = 1
    indicates a patient who had an obstetric trauma from a Cesarean
    section, while TPPS20 = 0 identifies a patient who had a C-section
    but no trauma complication.

-   For the Provider Indicators, the MEANs will contain a close
    approximation of the eventual overall observed indicator rates. The
    values will change slightly after PSSASP2 has applied additional
    parts of the indicator definitions.

-   N lists the number of observations in the dataset with non-missing
    values. For the six Area indicators, N for TAPSxx will be the same
    as the SUM. For the Provider Indicators, N will contain the
    denominator for the observed indicator rate.

## PSSPSP2

The purpose of this printout is to provide the observed rates for all
Provider-level Indicators. The default printout shows results by
provider, but other levels of output (as shown in Table 6) can be
specified as well. Note that risk-adjusted and smoothed rates are shown
in the output from the next program.

The printout from the PSSPSP2 program contains descriptive statistics on
the provider-level summary records for all of the numeric variables in
the output summary dataset. It will contain information for the newly
constructed OPPSxx rates, the PPPSxx denominators, and the TPPSxx
numerators.

-   The STRAT variable described in the descriptives table identifies
    the stratification level for the records in the output data set. The
    STRAT variable corresponds to the !STRLEVS parameter values that
    were specified (see item 5 in "[Changes]{.underline}" under the
    PSSPSP2 program). In this case, STRAT always assumes the value of
    16, since only the provider-level records are selected.

-   The N statistic for STRAT contains the number of records in the
    output summary data set. A TPPSxx numerator variable with a value
    for N that is lower than the N value for STRAT indicates that there
    were no outcomes of interest for some of the providers. Similarly, a
    PPPSxx denominator variable with a lower value for N than STRAT
    indicates that for some providers, there were no hospital discharges
    with the outcome of interest.

-   The MINIMUM value for the TPPS01-TPPS20, TPPS27-TPPS29 numerators
    will be zero since values of zero were assigned for observations
    that were part of the population for the rate denominator but did
    not have the particular outcome of interest to be included in the
    rate numerator.

> ![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
> *For the observed rates, the User should **NOT** report the MEANS
> displayed here, but instead should refer to the overall means in the
> output dataset that are also present in the subsequent LISTING. The
> MEANS given here are means of hospital means; i.e., all hospitals are
> given equal weight, regardless of the number of discharges in the
> different hospitals.*

-   The SUMs for the counter variables TPPSxx and PPPSxx will contain
    overall file totals for these data elements. The SUMs for the
    observed rates have no intuitive meaning.

If the !PRINT parameter is set to "Yes", the subsequent LISTING output
contains a complete dump of the output summary file. Listed for each
record are the stratification values, the PPPSxx population denominators
for the 23 indicators, the TPPSxx outcome numerators for the 23 Provider
Indicators, and the 23 OPPSxx observed rates.

## PSSPSP3

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
*The LISTING at the end of this program provides your **final output**.
(This printout appears if the !PRINT parameter is set to "Yes"-- the
default setting.) It lists the numerator and the denominator, along with
the observed, risk-adjusted, and smoothed rates for all indicators, as
shown in the following example.*

STRAT HOSPID AGECAT SEXCAT PAYCAT RACECAT TPPS04 PPPS04 OPPS04 RPPS04
SPPS04

0 . 1103 7322 .150642 .184167 .183908

16 67000 0 8 .000000 .097114 .166435

16 71000 13 85 .152941 .225124 .191035

16 72000 0 6 .000000 .117922 .168236

16 76000 27 225 .120000 .162791 .165709

16 81000 52 220 .236364 .228673 .205974

16 85000 21 159 .132075 .181800 .176450

16 87000 1 19 .052632 .087305 .160480

16 89000 3 23 .130435 .226091 .178231

16 91000 21 150 .140000 .187632 .179297

16 93000 40 279 .143369 .180632 .177203

16 95000 39 219 .178082 .226401 .204526

16 96000 14 82 .170732 .194382 .179237

16 104000 . 0 . . .

16 106000 4 23 .173913 .137757 .165792

16 108000 7 65 .107692 .175852 .172117

16 109000 33 223 .147982 .188629 .181584

16 111000 13 79 .164557 .166927 .169141

16 114000 71 420 .169048 .177468 .175694

16 115000 2 14 .142857 .158940 .169349

16 117000 36 452 .079646 .144308 .150487

16 118000 173 1276 .135580 .170824 .170781

16 119000 42 307 .136808 .175408 .173833

16 121000 10 107 .093458 .134601 .154905

16 124000 161 906 .177704 .205327 .200641

16 125000 9 80 .112500 .179932 .173853

16 128000 1 3 .333333 .351560 .174179

16 129000 49 282 .173759 .199062 .189534

16 130000 67 397 .168766 .202402 .194041

16 134000 52 256 .203125 .213217 .198052

16 137000 3 73 .041096 .098798 .145890

16 140000 22 164 .134146 .167299 .168723

16 141000 23 98 .234694 .256188 .205668

16 142000 60 336 .178571 .190744 .184747

16 143000 23 225 .102222 .149181 .157327

16 144000 11 61 .180328 .214140 .183644

Number of cases read: 36 Number of cases listed: 36

In this example printout, record 1 (with HOSPID = \".\") is the overall
average for the entire dataset (STRAT = 0). The remaining observations
are individual providers, or hospitals (STRAT = 16). Data will appear
under the column headers, AGECAT, SEXCAT, PAYCAT, and RACECAT, if you
specify these levels of aggregation (shown in Table 6).

You may wish to express the results in more understandable terms:

-   Multiply the rates by 100 to express them as a percentage (e.g.,
    .150642 \* 100 = 15.06%)

-   To create standardized rates or rates per 1,000 discharges, multiple
    the output by 1,000.

The descriptive statistics table is generated from the permanent
provider-based output file and is provided for trouble-shooting and
understanding your data, but not for reporting. The means are provided
just for the provider level summary records.

-   The N for all but the TPPSxx counter variables should contain the
    number of providers in the users database.

-   The MEANS, MINIMUMs, and MAXIMUMs have their normal meaning and
    provide comparisons among the different providers or hospitals in
    your database.

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
For the (observed, risk-adjusted, or smoothed) rates, the user should
**NOT** report the MEANS displayed here, but instead refer to the
overall means in the output dataset in the PROC PRINT labeled \"FINAL
OUTPUT.\" The MEANS given here are means of hospital means; i.e., all
hospitals are given equal weight, regardless of the number of discharges
in the different hospitals.

-   If the !PRINT parameter is set to "Yes", at the end of the printout
    is a LISTING on the final provider-based output file. Listed for
    each level of stratification are the stratifiers, the numerator and
    denominator totals for the observed rates, and the observed,
    risk-adjusted, and smoothed rates.

## PSSPSA2

The purpose of this printout is to provide the observed rates for all
Area-level Indicators. The default printout shows overall results and
results by area, but other levels of output (as shown in Table 7) can be
specified as well.

-   The printout from the PSSPSA2 program contains descriptives for all
    of the numeric variables in the output summary dataset. It will
    contain information for the newly constructed OAPSxx rates, the
    PAPSxx denominators, and the TAPSxx numerators. The MEANS table is
    generated from the permanent area-based output file. The means are
    provided just for the area-level summary records.

-   The STRAT variable described in the first row of the descriptives
    table identifies the stratification level for the records in the
    output data set. The STRAT variable corresponds to the !STRLEVS
    parameter values that were specified (see item 7 in
    "[Changes]{.underline}" under the PSSPSA2 program on page
    [24](#_Ref83545298)). In this case, STRAT always assumes the value
    of 8 since only the area-level records are selected.

-   The N statistic for STRAT contains the number of areas in the output
    summary data set. A TAPSxx numerator variable with a lower value for
    N than STRAT indicates that there were no outcomes of interest for
    some of the areas.

-   The MINIMUM value for the TAPSxx numerators will be one or higher.

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
For the observed rates, the user should **NOT** report the MEANS
displayed here, but instead should refer to the overall means in the
output dataset that are also present in the subsequent LISTING. The
MEANS given here are means of the area means; i.e., all areas are given
equal weight, regardless of the population in the different areas.

-   The SUMs for the counter variables TAPSxx and PAPSxx will contain
    overall file totals for these data elements. The SUMs for the
    observed rates have no intuitive meaning.

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
The LISTING at the end of this program provides your **final output**.
(This printout appears if the !PRINT parameter is set to "Yes"-- the
default setting.) It lists the numerator and the denominator, along with
the observed, risk-adjusted, and smoothed rates for all indicators, as
shown in the example output below.

> MSA AGECAT SEXCAT RACECAT TAPS25 PAPS25 OAPS25
>
> . 661 20953241 .000032
>
> 40 18 126441 .000142
>
> 320 0 218321 .000000
>
> 640 2 1263559 .000002
>
> 840 12 384977 .000031
>
> 1240 4 336991 .000012
>
> 1260 10 152657 .000066
>
> 1880 1 380689 .000003
>
> 1922 85 5254221 .000016
>
> 2320 45 682111 .000066
>
> 3362 219 4693524 .000047
>
> 3810 0 314252 .000000
>
> 4080 0 194868 .000000
>
> 4420 1 208797 .000005
>
> 4600 42 242882 .000173
>
> 4880 9 573920 .000016
>
> 5800 0 236345 .000000
>
> 7200 0 103970 .000000
>
> 7240 55 1599378 .000034
>
> 7640 0 110988 .000000
>
> 8360 4 129762 .000031
>
> 8640 0 175418 .000000
>
> 8750 1 84075 .000012
>
> 8800 1 214044 .000005
>
> 9080 0 140326 .000000
>
> 48001 0 55119 .000000
>
> 48003 0 12944 .000000
>
> 48005 14 80270 .000174
>
> 48007 0 22548 .000000

Record 1 (with MSA = \".\") is the overall average for the entire
dataset (STRAT = 0). The remaining observations are individual areas
(STRAT = 8).

You may wish to express the results in more understandable terms:

-   Multiply the rates by 100,000 to express them as a rate per 100,000
    population (e.g., .000032 \* 100,000 = 3.2 accidental
    puncture/lacerations per 100,000 population).

# Interpreting the Results 

The Patient Safety Indicators are not intended to be definitive quality
measures. Many factors can and do influence performance on quality
indicators and some of these factors are independent of quality of care.
The empirical analyses conducted by the research team during the
development of the PSI produced an estimation that generally less than
20% of total patient level variation for each QI is attributable to
actual provider-level differences. Though this number appears low, the
research team also estimated that most of this remaining provider-level
variation reflects true signal; that is, the observed performance is not
likely the result of random variation. The researchers also noted that
these true differences in provider performance are potentially
clinically important, in that they involve large numbers of patients,
severe and potentially preventable complications and adverse events,
and/or significant cost to the health care system.

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
Although these indicators are not intended and should not be used as
definitive measures of quality, they are useful low-cost screens that
can potentially illuminate differences between providers and areas that
may be addressable using quality and patient safety improvement
techniques.

Since very high rates may indicate quality problems, and since there are
no "right rates" established for most indicators, it is often best to
compare provider or area-level rates with other similar providers or
areas. These "peer groups" would ideally be as similar as possible in
potentially important factors, such as case-mix, socioeconomic status
and other demographics. Similar hospitals should perform similarly on
QIs. Potential characteristics that have been used to define peer groups
have been teaching status, bed capacity, socioeconomic status of the
population, and urban or rural location.

## Using Indicators in Combination

Performance on a single PSI often cannot reliably indicate actual
quality differences. Examining all the indicators together is likely to
produce a more complete picture of overall quality of care. Providers
that perform better (or worse) than average on one measure tend to
perform better (or worse) on others. In other words, performance on
indicators is often related, and performance on multiple similar
indicators could also be examined as summary indicators for an overall
picture of quality. Similarly, indicators may be related across
indicator types. *Groups of indicators have not been validated as sets,
but using them as such may be useful for exploration purposes.*

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
After performing all of the steps as previously outlined, users will
have three estimates of performance for each Provider-based PSI --
observed, risk-adjusted, and MSX smoothed (i.e., reliability-adjusted)
estimates. This section will outline how the different types of
estimates can be used.

## Observed Means

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
Examine observed rates as baseline measure of performance on the
indicators and to see the impact of risk-adjustment.

The interpretation of the observed (raw) PSI rates may be complicated by
concerns over noise and bias. However, the observed rates do not require
complex statistical methods as do the risk-adjusted and MSX smoothed
rates. For this reason, they are the most intuitive estimates of PSI
performance. Observed rates can be used as a baseline measure when
comparing to risk-adjusted and MSX smoothed rates, to determine the
impact of risk adjustment/smoothing.

Observed rates may fluctuate for some providers from year to year. While
some of these fluctuations may indicate true differences in performance,
others are due only to random chance (i.e., non-systematic differences
among providers in patient characteristics that are not observed, and
therefore cannot be adjusted for). For this reason, it is often
beneficial to examine observed rates for a given provider over several
consecutive time periods. This will help to diminish the chance of
inaccurately judging poorer than average or better than average
performance during one year as true performance.

## Risk-adjusted Rates. Provider PSIs Only

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
For most purposes, you will use the risk-adjusted rates.

Simply put, risk-adjusted rates are the estimated performance of
providers on the PSIs if those providers had an 'average' case mix. This
average case mix is estimated and included in the software using
estimates from 27 States in the HCUP Year 2000 SID databases. Estimates
of the average case mix do not reflect only the providers in the dataset
being analyzed, but rather the distribution in age, sex, modified DRG
and co-morbidity categories among the providers in the SID data.

Most Provider Indicators are risk adjusted using age, sex, modified DRGs
and co-morbidities. A few Provider Indicators cannot be adjusted using
DRGs since the population at risk is characterized by a few DRGs. These
are the OB related indicators.

For Transfusion reaction (PSI #16) the outcome of interest is a
relatively rare event and the observed rates will be extremely low. No
risk-adjustment or smoothing is performed for this indicator.

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
The output will not include any risk-adjusted or smoothed rates for PSI
#16, Transfusion reaction. The software will generate observed rates
only.

Users should compare risk-adjusted rates with the observed rates. This
will indicate the impact of risk adjustment and presumably case mix on
indicator performance. Providers with large changes in performance
between observed and risk-adjusted rates presumably have a more or less
complex case mix.

The construction of risk-adjusted rate uses the standard method with
logistic models of first estimating the predicted value for each
discharge, then subtracting the actual outcome from the predicted, and
averaging the difference for each provider (and adding in the overall
rate) to get the provider fixed effect estimate. The logistic model was
appropriate given the rare occurrence of many of the PSIs and the
dichotomous outcomes. The risk-adjustment model for each PSI accounts
for patient demographics (age, sex) and DRG/co-morbidity category. The
risk-adjusted rates reflect the estimated performance on the PSI for
each provider if that provider had the 'average' case mix among all
providers in the estimation sample.

Because the fixed effects are calculated indirectly with a logistic
model, the estimated risk-adjusted rates may be negative (that is, the
model does not require the rates to be between zero and one). This might
happen, for example, if the observed rate is close to zero, and the
provider has a more severe than average case mix. The model would
predict that the provider's performance with an 'average' case mix would
be less and subtract some adjusted amount from the observed rate. If
that observed rate is already nearly zero, the adjusted rate may be
negative. A negative rate means that the observed rate is close to zero,
and that the provider has a less-severe-than-average case mix. In order
to facilitate the interpretation of the estimates, the PSI module
imposes a lower bound of zero; i.e., negative values are set to zero.

## MSX Smoothed rates (Optional). Provider PSIs Only

The PSSASP3 program also yields the estimated MSX smoothed rates for
each PSI. These smoothed rates are estimated using multivariate signal
extraction (MSX). MSX is a smoothing technique similar to Bayesian
methods. Generally, indicators defined on relatively small populations
per provider or for relatively rare events are very noisy measures. In
other words, many other factors other than quality can influence the
observed rate. For factors that can be observed, such as the patient's
age or gender or DRG, risk adjustment can account for their influence.
There are many other clinical and non-clinical factors that cannot be
observed. The MSX method estimates how much of an impact random
differences in these factors across providers have on the observed rate.
The SAS program accomplishes this by adjusting toward the overall mean
according to the degree of reliability of the specific provider
indicator.

Just as risk-adjustment levels the playing field across providers by
\"equalizing\" patient characteristics, smoothing levels the playing
field by removing random variation in the measures across providers. In
essence, smoothing describes how persistent a provider\'s rate would be
from year to year. For example, smaller hospitals with fewer cases will
tend to be the best and worst performers on an indicator in a given
year, because a few cases can have a tremendous impact on the rates.
Compare the rates for these two hospitals:

  ------------------------------- -------------------- -------------------
  **Hospital A**                  **1999**             **2000**

  Numerator                       0                    1

  Denominator                     11                   12

  Observed rate                   0%                   8.3%

  Risk-adjusted rate              0%                   8.1%

  Smoothed rate                   3.3%                 3.5%

                                                       

  **Hospital B**                                       

  Numerator                       10                   12

  Denominator                     363                  454

  Observed rate                   2.8%                 2.6%

  Risk-adjusted rate              2.3%                 2.1%

  Smoothed rate                   2.9%                 2.8%
  ------------------------------- -------------------- -------------------

Looking at the observed and even the risk adjusted rates can be
misleading. Quality of care in Hospital A did not necessarily decline in
2000 compared to 1999. Similarly, quality of care in Hospital A is not
necessarily better than Hospital B in 1999, not is it worse than
Hospital B in 2000. Notice that smoothing affects the rates for Hospital
A much more than for Hospital B. In 1999, the smoothed rate is quite a
bit higher than the risk adjusted rate. And in 2000, Hospital A\'s
smoothed rate is quite a bit lower. Both smoothed rates have migrated
toward the mean. On the other hand, the smoothed rate for Hospital B is
much more stable across the years and it is more similar to the
risk-adjusted rate. Smoothing attempts to correct for random variations
by adjusting for differences in the reliability of a hospital\'s
estimate -- generally, reliability improves with a hospital\'s size.

![](media/image2.jpeg){width="0.2708333333333333in" height="0.1875in"}
The smoothed rates are intended to help you look for how best to present
the data. For example, if smoothed rates vary considerably from
risk-adjusted rates, you might wish to examine risk-adjusted performance
by combining data for several years rather than examining a single
year\'s performance, or just compare hospitals within peer groups. In
the example, above, you might choose to present rates separately by bed
size and over a longer period, e.g., 3-5 years, so that cases are
aggregated for smaller hospitals.

The MSX method estimates reliability in two ways: (1) a univariate
\"shrinkage\" estimator based on the unexplained patient level variation
for a single measure in a single year, and (2) a multivariate approach
that looks at provider performance among multiple indicators and across
multiple years for a single indicator. If providers that perform high in
one year also tend to perform high in the next, and providers that are
low in one indicator tend to perform low in other related indicators,
then the methods incorporate this information to improve the estimate of
how much of a provider's performance on a single indicator in a single
year is "signal" and how much is "noise". PSSASP3 reports the univariate
"signal" estimate, after removing the "noise".

These estimates are referred to as "smoothed" estimates because when the
raw data is reported annually on a graph, for example, the line
connecting the points may show massive fluctuations, seemingly with no
apparent pattern. Some of these fluctuations are due to random
differences in factors that influence performance, so once the impact of
these factors is removed, fluctuations are reduced, or smoothed out.
Improvements in performance will still be observed, however, they will
only be observed when it is likely that these improvements are actually
true differences, and not simply random variation.

The estimates of how related the Patient Safety Indicators are among
measures and over time for a typical provider are based on estimates
using the 27 states in the HCUP Year 2000 SID databases. Therefore,
PSSASP3 does not require multiple providers, measures, and years of data
to operate. Instead shrinkage estimates were calculated from the
combination of 27 statewide HCUP Year 2000 SID datasets to which the MSX
had been applied. These shrinkage estimates are the best estimates of
the impact that MSX smoothing would have on a particular PSI if MSX
could be applied to the dataset being analyzed. These shrinkage
estimates are then applied to the adjusted rates for each PSI, giving
'smoothed' estimates of the rates.

The smoothed estimates represent the best guess of what the provider
performance would be for any given PSI if the data contained only a
minimal amount of noise. This has several implications. First, users can
be more certain that changes observed over time represent true
differences in performance, rather than random variation. Second, in any
given year, users can be more certain that the rate does not reflect
only random noise. This can best be seen by comparing the smoothed
estimates with the observed raw rates, which will indicate the impact of
MSX on that indicator. A large impact means that the observed rate of
the indicator is less precise, meaning it contains more noise relative
to other indicators sustaining less impact. Low precision can result
from small numbers of observations, or for relatively rare events.
Therefore, the impact of the MSX estimate will in general be greater for
small providers and for infrequent events. For providers with small
numbers of cases, the MSX estimates may be the same over time as the
estimates are being "shrunk" to an overall mean. Plotting the MSX
estimates over time will reflect more persistent performance from
year-to-year, and the correlations among indicators will generally be
stronger.

## Comparing Observed, Risk-adjusted and Smoothed Rates. Provider PSIs Only

The purpose of the analysis determines which rates the user should look
at in evaluating the performance of a provider. If the user's primary
interest is to focus on a particular provider without any comparisons to
other providers, simply examine the overall observed rate for the entire
provider, as well as further breakdowns by age, sex, payer, and
race/ethnicity which are the output created by the PSSASP2 programs.
Trend data are recommended for identifying changes over years.

If the purpose of the analysis is to compare the performance of a
particular provider with national, state, or regional averages or
performance of other selected providers, then both observed and
risk-adjusted rates should be examined. Variation in observed rates
across providers is attributable to a variety of factors including
differences in patient case mix or population demographics, disparity in
access to and quality of care, and other provider characteristics
('systematic factors'), and random factors (non-systematic factors or
'noise'). Comparing observed and risk-adjusted rates can reveal if there
is any difference between the provider's population and the population
of other providers. If the difference is minimal, one can compare the
observed rate with the overall average across all providers. However, to
account for differences in patient case mix or population demographics
among different providers, risk-adjusted rates should be used for
provider comparisons.

After removing the impact of patient case mix or population
demographics, if users want to examine potential existence of random
factors, comparisons can be made between the risk-adjusted rates and the
smoothed rates to determine if the differences in risk-adjusted rates
across providers are due to systematic, as opposed to random, factors.
The following two tables provide guidance on how to interpret
differences in observed, risk-adjusted, and smoothed rates.

## 

## Comparing Observed Rates with Risk-adjusted Rates

*Purpose: To identify if there is any difference in the patient case mix
of the provider relative to that of all providers combined*

+------------------------+---------------------------------------------+
| Observed rate **\>**   | The provider's patient population for the   |
| Risk-adjusted rate     | condition or procedure has a ***higher***   |
|                        | risk of complication/adverse event due to   |
|                        | its case mix (for example, older or a       |
|                        | greater proportion of a higher-risk DRG/    |
|                        | comorbidity).                               |
+------------------------+---------------------------------------------+
| Observed rate **\<**   | The provider's patient population for the   |
| Risk-adjusted rate     | condition or procedure has a ***lower***    |
|                        | risk of complication/adverse event due to   |
|                        | its case mix (for example, younger or a     |
|                        | greater proportion of a lower-risk          |
|                        | DRG/comorbidity).                           |
+------------------------+---------------------------------------------+
| Observed rate **=**    | Mortality indicators:                       |
| Risk-adjusted rate     |                                             |
|                        | The provider's patient case mix for the     |
|                        | condition or procedure is similar to other  |
|                        | providers', suggesting that patient         |
|                        | composition is not a contributing factor to |
|                        | the provider's performance for the          |
|                        | complication/adverse event indicator.       |
+------------------------+---------------------------------------------+

## Comparing Risk-adjusted Rates with Smoothed Rates (Optional)

Purpose: To determine if differences in risk-adjusted rates across
providers are due to systematic or random factors after patient case mix
or demographic composition is taken into account.

  ------------------------- ---------------------------------------------
  Risk-adjusted rate        The provider's risk-adjusted rate is more
  ***similar to*** Smoothed precise, an accurate reflection of the
  rate                      provider's systematic ('true') rate. If there
                            is any difference between the risk-adjusted
                            rate and the overall average^1^, such
                            difference is likely to be due to systematic
                            factors.

  Risk-adjusted rate        The provider's risk-adjusted rate is less
  ***different from***\     precise^2^; that is, some of the difference
  Smoothed rate             between the risk-adjusted rate and the
                            overall average is due to random ('noise')
                            factors. The smoothed rate is thus a more
                            accurate estimate of the systematic rate than
                            the risk-adjusted rate. Comparing the
                            smoothed rate to the overall provider average
                            reveals more accurately the 'true'
                            performance of the provider.
  ------------------------- ---------------------------------------------

Notes: 1. The overall provider average refers to the weighted average
risk-adjusted rates across all providers.

2\. The risk-adjusted rates for providers with small population are
generally less precise.

Generally, subtracting the observed, risk-adjusted and smoothed rates
can help to reveal differences among these rates. To get a sense of the
magnitude, the most straightforward approach is to estimate the
difference in terms of the number of cases in the numerator. For
example, for a hospital with 1000 cases, a difference of -0.005 between
the observed rate and risk-adjusted rate would mean five adverse events.
Whether the difference between rates is statistically meaningful will
depend on the number of discharges in the population at risk, and the
sampling variability for each indicator. Users can apply a rough rule of
thumb to estimate the required difference: 1.4\* SQRT(p\*(1-p)/N), where
p is the rate and N is the denominator of the indicator.

For example, if the observed rate for an indicator is p=0.045 and the
population at risk is N=200, applying the formula to these numbers will
produce: 1.4\* SQRT(0.045\*(1-.045)/200) = 0.0205. That is, for the
risk-adjusted rate to be significantly different from the observed rate,
the absolute difference between the two rates has to be equal to or
greater than 0.0205.

## Confidence Intervals 

The software does not include a procedure for calculating confidence
intervals for the PSIs. Any such procedure should be evaluated for
robustness depending on the provider's denominator and rate. Users may
request a supplementary module to calculate a 95% CI (PSSPSP3CI.SAS) for
each PSI and provider using a procedure based on a normal approximation
that is generally appropriate. The module can be requested by sending an
e-mail to <support@qualityindicators.ahrq.gov> and specify "PSI
Confidence Interval Syntax Request" in the subject line and indicate in
the body of the e-mail you would like the SAS syntax.

## Computing Expected Rates (Optional)

While the risk-adjusted rate assumes an "average" case-mix (but the
provider's actual performance for each patient group), an expected rate
assumes an "average" performance for each patient group (but the
provider's actual case-mix). The relationship between the two rates is
given by the formula:

Risk-adjusted rate = (Observed Rate -- Expected Rate) + Population Rate.

PSI Version 2.1, Revision 2 calculates an expected rate by subtracting
the risk-adjusted rate from the observed rate and adding the population
rate. For example, if the risk-adjusted rate is 5.1%, the observed rate
is 4.5% and the population rate is 6.0%, then the expected rate is (4.5
-- 5.1) + 6.0 = 5.4%. The provider performed better than expected given
the provider's actual case-mix (5.4% vs. 4.5%, or -0.9%). The
risk-adjustment model assumes that the provider would also perform
better than expected (and to the same extent) if the provider had an
"average" case-mix (6.0% vs. 5.1%, or -0.9%).

# Benchmark Timings

The benchmark runtimes given below are from runs made on a Microsoft
Windows 98 PC, with an Intel Pentium III, 1.2 GHz processor, and 512MB
of RAM. The dataset used contained 300,000 records with 10 diagnosis
fields and 6 procedure fields.

  ----------------------------------------- -----------------------------
  **Step**                                  **Run time (in seconds)**

  Run PSSPS1                                1,980

  Run PSSPSP2                               29

  Run PSSPSP3                               1,578

  Run PSSPSA2                               23
  ----------------------------------------- -----------------------------

# User Support and Information

Technical assistance is available, through an electronic user support
system monitored by the QI support team, to support users in their
application of the PSI software. The same e-mail address may be used to
communicate to AHRQ any suggestions for PSI enhancements, general
questions, and any QI related comments you have. AHRQ welcomes your
feedback.

The Internet address for user support and feedback is:
<support@qualityindicators.ahrq.gov>

AHRQ also offer a listserv to keep you informed on the Quality
Indicators (QIs). The listserv is used to announce any QI changes or
updates, new tools and resources, and to distribute other QI related
information. This is a free service. Simply follow the process described
below to begin receiving important QI information. All you need is a
computer, Internet access, and an E-mail address. It works just like
other electronic distribution lists.

Here's how to register:

1.  Send an E-mail message to: <listserv@qualityindicators.ahrq.gov>.

2.  On the subject line, type: Subscribe. For example:

> Subscribe

3.  In the body of the message type: sub Quality_Indicators-L and your
    full name. For example:

> sub Quality_Indicators-L John Doe

4.  You will receive a message confirming that you are signed up.

If you have any questions, contact AHRQ QI Support at the e-mail noted
above. You should receive an automatic response e-mail message
confirming receipt of your e-mail. If you do not receive a confirmation
message, call (888) 512-6090.

####### 

# Appendix A: Log of Revisions to PSI Documentation and Software Version 2.1, Revision 2

The following table summarizes the revisions made to the PSI software,
software documentation and the Guide to Patient Safety Indicators
(Guide) document in release version 2.1, revision 2. The table lists the
component(s) affected by the change and a short summary of the changes
that were made.

+-----------+----------------------------------------------------------+
| ***Com    | ***Changes***                                            |
| ponent*** |                                                          |
+===========+==========================================================+
| Guide     | 1.  Modified documentation to reflect changes in         |
|           |     indicators associated with ICD-9-CM coding updates   |
|           |     for FY 2004 (effective 10-1-2003). See separate      |
|           |     documentation for specific details.[^6]              |
|           |                                                          |
|           | 2.  Changed syntax of \"hospital-level\" to              |
|           |     \"provider-level\" throughout the documentation.     |
|           |                                                          |
|           | 3.  Added PSI number to each Indicator name.             |
|           |                                                          |
|           | 4.  Updated empirical results for Table 1, and limited   |
|           |     contents to Provider-level PSIs.                     |
|           |                                                          |
|           | 5.  Added Table 2, listing Area-level PSIs.              |
|           |                                                          |
|           | 6.  Added caption for Table 3, Indicators and Use of     |
|           |     External Cause-of-Injury Codes.                      |
|           |                                                          |
|           | 7.  Modified PSI #2 (death in low mortality DRGs). The   |
|           |     indicator is reported as a single measure, but also  |
|           |     stratified by type of DRG: adult medical, pediatric  |
|           |     medical, adult surgical (with OR procedure), adult   |
|           |     surgical (without OR procedure), pediatric surgical  |
|           |     (with OR procedure), pediatric surgical (without OR  |
|           |     procedure), obstetric and psychiatric. A list of low |
|           |     mortality DRGs by type is included PSI Guide.        |
|           |                                                          |
|           | > Impact: Among the low mortality DRGs, about 25% of the |
|           | > discharges and 60% of the deaths are "adult medical"   |
|           | > DRGs. Psychiatric DRGs also have a higher share of     |
|           | > deaths (10%) than discharges (6%). Death among the     |
|           | > other DRG types is very rare (0.1% or less). Few low   |
|           | > mortality surgical DRGs do not have an operating room  |
|           | > procedure, so the adult or pediatric surgical DRG      |
|           | > (without OR procedure) will generally be missing or    |
|           | > zero for most hospitals. Modified PSI #2, Death in     |
|           | > Low-mortality DRG, to split the adult and pediatric    |
|           | > surgical strata into separate strata for cases with    |
|           | > operating room procedures and cases without operating  |
|           | > room procedures.                                       |
|           |                                                          |
|           | 8.  Modified PSI #14, Postoperative Wound Dehiscence, to |
|           |     include only OR procedures in the definition of      |
|           |     abdominopelvic surgery.                              |
|           |                                                          |
|           | > Impact: Small (less than 1%) decrease in the           |
|           | > denominator and resulting small increase in the rate   |
|           | > due to exclusion of a low-risk procedure.              |
|           |                                                          |
|           | 9.  Modified PSI #17, Birth Trauma, to exclude preterm   |
|           |     infants with subdural or cerebral hemorrhage or      |
|           |     osteogenesis imperfecta infants with injury to       |
|           |     skeleton from the numerator only. NOTE: The infants  |
|           |     remain in the population at risk for other types of  |
|           |     birth trauma.                                        |
|           |                                                          |
|           | > Impact: Small (less than 1%) increase in the           |
|           | > denominator and resulting small decrease or no impact  |
|           | > in the rate (i.e. the risk of other types of birth     |
|           | > trauma for these two populations is less than or no    |
|           | > different than for other births).                      |
|           |                                                          |
|           | 10. Added three new Indicators #27-29, to include        |
|           |     third-degree lacerations for each of three types of  |
|           |     delivery: Vaginal with and without instruments, and  |
|           |     Cesarean.                                            |
|           |                                                          |
|           | > Impact: The rate for OB Trauma is generally 5-10%      |
|           | > higher when including 3^rd^ degree lacerations         |
|           |                                                          |
|           | 11. Limited the surgical DRG inclusion criteria to major |
|           |     OR procedures for PSI #1, 8-13, all of which deal    |
|           |     with postoperative illness or injury.                |
|           |                                                          |
|           | > Impact: Medium (1-4%) decrease in the denominator. The |
|           | > impact on the rate varies by indicator. PSIs 1, 8 and  |
|           | > 9 have a medium (1-3%) increase in the rate. PSIs 10   |
|           | > and 12 have a small (less than 1%) decrease in the     |
|           | > rate. PSIs 11 and 13 have a medium (3-4%) decrease in  |
|           | > the rate.                                              |
|           |                                                          |
|           | 12. Modified PSIs #1, 3, 5, 6, 7, 8, 9, 10, 11, 12,      |
|           |     13, 15. 16 to exclude discharges with a PSI-defining |
|           |     secondary diagnosis and a different PSI-defining     |
|           |     principal diagnosis (but within the same PSI         |
|           |     definition).                                         |
|           |                                                          |
|           | > Impact: Small (less than 1%) decrease in the           |
|           | > denominator. The impact on the rate varies by          |
|           | > indicator. PSIs 1, 3, 6, 7, 8, 10, 11, 13 and 16 have  |
|           | > a small (less than 1%) increase in the rate. PSI 9 has |
|           | > a small (less than 1%) decrease in the rate. PSI 15    |
|           | > has a medium (2-3%) decrease in the rate. PSIs 5 and   |
|           | > 12 have a large (5-9%) decrease in the rate.           |
|           |                                                          |
|           | 13. Modified PSIs #8, 9, 11, 12 to exclude discharges    |
|           |     where the only OR procedure is a PSI-related         |
|           |     procedure.                                           |
|           |                                                          |
|           | > Impact: Small (less than 1%) decrease in the           |
|           | > denominator. The impact on the rate varies by          |
|           | > indicator. PSI 11 has a small (less than 1%) decrease  |
|           | > in the rate. PSI 9 has a medium (1-2%) decrease in the |
|           | > rate. PSIs 8 and 12 have a large (15-65%) decrease in  |
|           | > the rate.                                              |
|           |                                                          |
|           | 14. Modified PSIs #8, 9, 11, 12, 14 to exclude           |
|           |     discharges where a PSI-related procedure precedes    |
|           |     the denominator-defining OR procedure.               |
|           |                                                          |
|           | > Impact: Small (less than 1%) decrease in the           |
|           | > denominator. The impact on the rate varies by          |
|           | > indicator. PSI 9 has a large (65-70%) increase in the  |
|           | > rate. PSIs 11 and 12 have a small (less than 1%)       |
|           | > decrease in the rate. PSI 8 has a medium (3-4%)        |
|           | > decrease in the rate. PSI 14 has a large (8-9%)        |
|           | > decrease in the rate.                                  |
|           |                                                          |
|           | 15. Modified Area level PSI #24, Postoperative Wound     |
|           |     Dehiscence, to drop the requirement that the wound   |
|           |     reclosure occurs in a discharge with a procedure     |
|           |     code of abdominopelvic surgery.                      |
|           |                                                          |
|           | > Impact: Numerator increases by about 40%.              |
|           |                                                          |
|           | 16. Added code 72.79 to the definition of                |
|           |     instrument-assisted delivery in PSI #18, 19.         |
|           |                                                          |
|           | > Impact: Transfers about 33% of the denominator from    |
|           | > PSI 19 to PSI 18. Because the OB Trauma rate for these |
|           | > cases is higher than average for PSI 19 and lower than |
|           | > average for PSI 18, and because the OB Trauma rate for |
|           | > PSI 19 is lower than PSI 18, the rate for both         |
|           | > indicators decreases by 3-10%.                         |
+-----------+----------------------------------------------------------+

+-----------+----------------------------------------------------------+
| ***Com    | ***Changes***                                            |
| ponent*** |                                                          |
+===========+==========================================================+
| Software  | 1.  Implemented syntax changes associated with ICD-9-CM  |
| (SAS and  |     coding updates from FY 2004 (effective 10-1-2003).   |
| SPSS)     |     See separate documentation on ICD-9 coding updates   |
|           |     for specific details.                                |
|           |                                                          |
|           | 2.  Implemented all syntax changes required to implement |
|           |     the indicator modifications (noted above under       |
|           |     Guide) and incorporated the related documentation in |
|           |     the Software manuals.                                |
|           |                                                          |
|           | 3.  Modified the age, DRG and co morbidity aggregations  |
|           |     used in the risk-adjustment to reflect the new rates |
|           |     and to group the DRGs by MDC (including an           |
|           |     MDC-specific other category).                        |
|           |                                                          |
|           | 4.  Added the calculation and reporting of the expected  |
|           |     rate at the stratification level selected by the     |
|           |     user. The SAS (PSSASP3.SAS) and SPSS (PSSPSP3.SPS)   |
|           |     software now calculates the risk-adjusted rate, the  |
|           |     expected rate and the smoothed rate. The rates are   |
|           |     saved in the output file. The user also has the      |
|           |     option to print the rates or save the rates in a     |
|           |     comma-delimited ASCII file.                          |
+-----------+----------------------------------------------------------+
| Software  | 1.  Inserted "PS" in format names for age, sex, DRG and  |
| (SAS)     |     co morbidity aggregations in SAS programs to         |
|           |     distinguish these formats from similarly named       |
|           |     formats used by other indicator software.            |
+-----------+----------------------------------------------------------+

####### 

# Appendix B: ICD-9-CM and DRG Coding Updates in PSI Release Version 2.1, Revision 2

The following changes were implemented in version 2.1, revision 2 of the
Patient Safety Indicator PSI software code (both SAS and SPSS) and
reflect changes to indicator definitions based on updates to ICD-9-CM
and DRG codes for Fiscal Year 2004 (effective 10-1-2003). All changes
noted below have been incorporated into the software syntax, software
documentation and the Guide to Patient Safety Indicators. With this
software update, the PSI software definitions now incorporate ICD-9-CM
codes valid from October 1, 1994 through September 30, 2004.

+--------------+---------------+--------------------------------------+
| ***Indicator | **            | ***Change***                         |
| Name (#)***  | *Component*** |                                      |
+==============+===============+======================================+
| Failure to   | Denominator   | Added new (FY 2004) code 480.3       |
| Rescue\      | (exclusion,   | \"Pneumonia due to SARS-associated   |
| (PSI #4)     | viral         | coronavirus\" to the viral pneumonia |
|              | pneumonia)    | exclusion criteria (for FTR -        |
|              |               | pneumonia)                           |
|              |               |                                      |
|              |               | Expected impact on rate: negligible  |
+--------------+---------------+--------------------------------------+
| Failure to   | Denominator   | Added new (FY 2004) code 785.52,     |
| Rescue\      | (inclusion,   | \"Septic shock\" to the denominator  |
| (PSI #4)     | shock or      | inclusion criteria (for FTR - shock  |
|              | cardiac       | or cardiac arrest)                   |
|              | arrest)       |                                      |
|              |               | Expected impact on rate: negligible  |
+--------------+---------------+--------------------------------------+
| Iatrogenic   | Denominator   | Added new (FY 2003) DRG code 525     |
| P            | (exclusion,   | \"Heart assist system implant\" to   |
| neumothorax\ | cardiac       | the cardiac surgery exclusion        |
| (PSI #6)     | surgery)      | criteria.                            |
|              |               |                                      |
|              |               | Expected impact on rate: negligible  |
+--------------+---------------+--------------------------------------+
| P            | Denominator   | Added new (FY 2004) code 68.39       |
| ostoperative | (inclusion,   | \"Other subtotal abdominal           |
| Wound        | a             | hysterectomy, NOS\" to denominator   |
| Dehiscence\  | bdominopelvic | inclusion criteria for               |
| (PSI #14)    | surgery)      | abdominopelvic surgery.              |
|              |               |                                      |
|              |               | Expected impact on rate: negligible  |
+--------------+---------------+--------------------------------------+
| Birth Trauma | Numerator     | Added new (FY 2004) code 767.11      |
| (PSI #17)    |               | \"Epicranial subaponeurotic          |
|              | (inclusion,   | hemorrhage (massive)\" to numerator  |
|              | birth trauma) | inclusion criteria for birth trauma. |
|              |               |                                      |
|              |               | Expected impact on rate: may         |
|              |               | increase slightly                    |
+--------------+---------------+--------------------------------------+
| Birth Trauma | Denominator   | Added new (FY 2004) codes 767.11     |
| (PSI #17)    | (inclusion,   | "Epicranial subaponeurotic           |
|              | liveborn)     | hemorrhage (massive)" and 767.19     |
|              |               | "Other injuries to scalp" and new    |
|              |               | categories 766.2x, Disorders         |
|              |               | relating to long gestation and high  |
|              |               | birth weight; 770.8x, Other          |
|              |               | respiratory conditions of fetus and  |
|              |               | newborn (FY 2003); 771.8x,           |
|              |               | Infections specific to the perinatal |
|              |               | period (FY 2003); 772.1x, Fetal and  |
|              |               | neonatal hemorrhage (FY 2002); and   |
|              |               | 779.8x, Other and ill-defined        |
|              |               | conditions originating in the        |
|              |               | perinatal period (FY 2003).          |
|              |               |                                      |
|              |               | Expected impact on rate: negligible  |
+--------------+---------------+--------------------------------------+
| Multiple     | Shock         | Added new (FY 2004) code 785.52,     |
| Indicators   | exclusion     | "Septic shock" to the Shock          |
|              |               | exclusion criteria for the           |
|              |               | applicable PSIs                      |
|              |               |                                      |
|              |               | Expected impact on rate: negligible  |
+--------------+---------------+--------------------------------------+
| Multiple     | Trauma        | Added new (FY 2004) codes 850.11     |
| Indicators   | exclusion     | "Concussion-brief coma \< 31         |
|              |               | minutes" and 850.12 "Concussion -    |
|              |               | brief coma 31-59 minutes" to the     |
|              |               | Trauma exclusion criteria for the    |
|              |               | applicable PSIs                      |
|              |               |                                      |
|              |               | Expected impact on rate: negligible  |
+--------------+---------------+--------------------------------------+
| Multiple     | Immu          | Added new (FY 2004) code 37.51,      |
| Indicators   | nocompromised | \"Heart transplantation\" to the     |
|              | state         | immunocompromised state exclusion    |
|              | exclusion     | criteria for the applicable PSIs     |
|              |               |                                      |
|              |               | Expected impact on rate: negligible  |
+--------------+---------------+--------------------------------------+
| Multiple     | Surgical      | Added new (FY 2004) DRG codes        |
| Indicators   | discharges    | 528-540 to the surgical discharges   |
|              | denominator   | inclusion criteria for the           |
|              | inclusion     | applicable PSIs.                     |
|              |               |                                      |
|              |               | Expected impact on rate: negligible; |
|              |               | may decrease rates on FY04 data from |
|              |               | Revision 1                           |
+--------------+---------------+--------------------------------------+
| Multiple     | Cancer        | Added new (FY 2004) DRG codes        |
| Indicators   | discharges    | 539-540, Lymphoma & leukemia with    |
|              | denominator   | major operating room procedure with  |
|              | exclusion     | and without complications,           |
|              |               | respectively, to the cancer          |
|              |               | exclusion criteria for the           |
|              |               | applicable PSIs.                     |
|              |               |                                      |
|              |               | Expected impact on rate: negligible  |
+--------------+---------------+--------------------------------------+

[^1]: Available at
    <http://www.qualityindicators.ahrq.gov/psi_download.htm>.

[^2]: SPSS is a statistical program distributed by SPSS, Inc.
    ([http://www.spss.com](http://www.spss.com/)). The company may be
    contacted directly regarding the licensing of their product. SPSS,
    Inc. does not have any affiliation with AHRQ nor involvement in the
    development of the AHRQ QIs.

[^3]: Federal Information Processing Standard, as defined by the U.S.
    Department of Commerce, National Institute of Standards and
    Technology (formerly National Bureau of Standards).

[^4]: Federal Information Processing Standard, as defined by the U.S.
    Department of Commerce, National Institute of Standards and
    Technology (formerly National Bureau of Standards). Note: Certain
    independent cities (Baltimore City, Carson City and St. Louis City),
    and areas within Hawaii and Virginia, are assigned to different area
    groupings in the Modified FIPS categories as compared to the U.S.
    Census Bureau groupings. The AHRQ QI software uses the Modified FIPS
    code assignment of these areas. Failure to use the Modified FIPS
    codes assignment will result in the use of incorrect denominator
    estimates for Area Indicators.

[^5]: Variables PRDAY1 to PRDAY30 are defined as the number of days from
    date of admission to date of procedure for each procedure. For
    example, if the patient was admitted on June 15^th^ and had two
    procedures - the principal procedure on June 15^th^ and a second
    procedure on June 18^th^ -- then the value of PRDAY1 would be zero
    (0) and the value of PRDAY2 would be three (3). For more
    information, consult the HCUP data documentation at
    <http://www.hcup-us.ahrq.gov/db/vars/prdayn/nisnote.jsp> .

[^6]: Updates to Version 2.1, Revision 2 -- ICD-9-CM Coding Updates,\"
    <http://www.qualityindicators.ahrq.gov/psi_download.htm>