# Presentation: 098717

##  National Hospital Discharge Survey (NHDS) and National Survey of Ambulatory Surgery (NSAS)

- 2006 Data Users Conference
- July 10, 2006
- 3:30pm-5:00pm
- Session #15

## NHDS:  Overview
Carol DeFrances, PhD

Analytic Issues
Karen Lees, MPH

Examples of Research
Jean Kozak, PhD

Accessing Data
Marni Hall, PhD

New Directions
Bob Pokras, MA

**NHDS:  Overview**
- Carol DeFrances, PhD
**Analytic Issues**
- Karen Lees, MPH
**Examples of Research**
- Jean Kozak, PhD
**Accessing Data**
- Marni Hall, PhD
**New Directions**
- Bob Pokras, MA

**Session Overview**

## Overview of the National Hospital Discharge Survey(NHDS)

- Carol DeFrances, PhD

**Notes:**
Good afternoon.  My name is Carol DeFrances and I will be giving you a brief overview of  the National Hospital Discharge Survey.

## NHDS Survey Years

- Conducted annually 1965-present
- Latest data available:  2004
- 2005 will be available this Winter

**Notes:**
The National Hospital Discharge Survey (NHDS) was first conducted in 1965 and is the longest continuing national survey of hospital inpatients.  

The NHDS is also the only nationally representative sample of inpatient discharges.

The most current data available are for 2004.  The 2005 data will be available in the Winter 2007.

## NHDS Survey Design

- Scope and coverage:
- Short stay, non-Federal hospitals
- ALOS < 30 days
- General and children’s general hospitals

**Notes:**
The NHDS is a national probability sample designed to meet the need for information on characteristics of inpatient discharges from non-Federal short-stay hospitals in the United States.

Only general hospitals, children’s general hospitals, or hospitals with an average length of stay of fewer than 30 days for all patients are included.

Federal, military  and Dept. of Veterans Affairs hospitals, hospital units of institutions such as prisons, and hospitals with fewer than 6 staffed beds are excluded. 

## NHDS Sampling Plan

- Three stage design:
- Geographic units
- Hospital
- Discharge

**Notes:**
Since 1988, the NHDS uses a modified three-stage design:
Units selected at the first stage consist of either hospitals or geographical areas, such as counties, groups of counties, or metropolitan statistical areas in the 50 States and the District of Columbia.  

At the second stage, hospitals are selected from within a sampled geographical area.

At the third stage, discharges are selected within sampled hospitals using systematic random sampling.

## NHDS Sample Size

- Hospitals:
- About 500 hospitals sampled per year
- Discharges:
- Over 300,000 sampled per year

**Notes:**
The hospital sample size is on average about 500 hospitals.  For the 2005 NHDS, we have a sample of 501 hospitals.

We collect information on over 300,000 samples discharges per year.

## NHDS Data Collection

- Manual hospitals - 56%
- Automated hospitals - 44%
- Overall response rate for the 2004 NHDS – 92%

**Notes:**
Let me point out that the NHDS is voluntary.   Hospitals who participate do it one of two ways:
We have a manual component.  About 56% of the sampled hospitals chose to participate this way.
We also  have an automated component.  About 44% of the sampled hospitals have elected this option.  
I should mention here that since the implementation of HIPAA (Health Insurance Accountability and Portability Act) more hospital have elected to provide us automated data.

The overall response rate for the 2004 NHDS was 92%.  Pre-HIPAA the NHDS response rate was 94% or better.  Post-HIPAA, we have fared a little worse.

## NHDS Manual Data Collection

- NCHS – Statistical Design
- Census Bureau – Field Work
- Contractor – Coding and Data Entry

**Notes:**
For the manual data collection:

NCHS does all the statistical design and coordinate with Census Bureau in the collection of the data.

It is the Census Bureau conducts the actual field work in contacting and visiting the hospitals.   Some hospitals collect the data themselves and then turn the information over the Census Bureau.  In others, Census Field Staff go directly into the hospital and gather the information from medical records.

Data collected by the Census Bureau is sent to the contractor, Constella Group, for coding and data entry.

The completed manual file is sent to NCHS for editing and estimation.

## NHDS Automated Data Collection

- Electronic files obtained from:
- States
- Commercial firms
- Individual hospitals

**Notes:**
On the automated side, NCHS obtains  electronic data files for sampled hospitals from various State data systems, commercial firms, or from the hospital themselves.

The automated data files comes directly to NCHS and is processed by NHDS staff.

Some of automated data received are sampled and some of the data are not.  The unsampled data are sampled at NCHS.

## NHDS Data Processing

- NCHS:
- Editing
- Estimation

**Notes:**
At NCHS, the manual data are combined with the sampled automated data.  The records are then edited for discrepancies.

Once the edits are completed, imputations are done for age, sex, and average length of stay  for records missing these variables.

After the imputations are completed, the data are weighted to produce nationally representative estimates.

## NHDS Estimation

- Weight:
- Inverse of the probability of selection
- Adjustments for non-response
- Population weighting ratio adjustment

**Notes:**
The weighting procedure produces essentially unbiased national estimates and has 3 basic components:

Inverse of the probability of sample selection.

Adjustment for non-response.

Population weighting ratio adjustments.

## Variables onNHDS Public Use Data Files

**Notes:**
I just want to mention the variables on the public use files.  

## Patient Data

- Age
- Sex
- Race
- Expected source of payment
- Discharge status
- Marital status

**Notes:**
We collect Patient Data such as:

Age

Sex

Race

Expected source of payment

Discharge status

Marital status

##  Hospital Characteristics

- Geographic region
- Bed size
- Ownership

**Notes:**
The NHDS collects information on Hospital Characteristics such as: 

Geographic region

Bed size

Ownership

## Medical Data

- International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM)
- Diagnoses  (up to 7)
- Procedures (up to 4)

**Notes:**
The medical data are coded to ICD-9-CM.

With respect to Medical Data, the NHDS collects up to 7 diagnoses and 4 procedures. 

Karen Lees will elaborate more about the diagnoses and procedure data. 

## Additional Variables

- Days of care
- Month of discharge
- Diagnoses Related Group (DRG)
- Weight

**Notes:**
Additional variables on the public use file include:

Days of care

Month of charge

DRG - Diagnosis Related Groups

Weight - For making national estimates

## New Variables for NHDS

- Available beginning in the 2001 NHDS:
- Source of Admission
- Type of Admission

**Notes:**
Beginning with  the 2001 NHDS data collection, two new variables,  source of admission and type of admission were added.

## New Variables for the NHDS

- Beginning to collect with the 2007 NHDS:
- Admitting Diagnosis
- Present on Admission checkbox for all seven diagnoses collected

**Notes:**
Admitting diagnosis and a present on admission checkbox for all of the diagnosis variables are being added to the UB04 which becomes effective in the Spring of 2007.  So we will now be able to collect these variables in the NHDS.  However, we are not sure when the estimates will be available.

## Analytic Issues

-  Karen Lees, MPH

**Notes:**
Good afternoon.  I’m Karen Lees, and I’m gong to discuss some analytic issues that you need to be aware of when you use NHDS data.

## Topics

- Utilization measures
- Medical coding system
- Statistical issues

**Notes:**
I’ll cover measures of hospital utilization that can be obtained from the survey, including how they are defined and some cautions about using them.   

I’ll also discuss the medical coding systems and some statistical issues:  weighting, reliability of data, and standard errors. 

## 
NHDS provides data on

hospitalizations
 not people

**NHDS provides**** data on**
*hospitalizations*
-  not people

**Notes:**
The first thing you need to keep in mind is that the NHDS provides data about hospitalizations, not people.  The survey data do not indicate whether a particular hospitalization is the first one or the tenth one a person had during the year.  So NHDS data can NOT tell you how many PEOPLE were hospitalized in a year for heart disease, they can only tell you how many hospitalizations there were for heart disease. 

##    Measures Include

- Discharges
- Days of care
- Average length of stay
- Diagnoses
- Surgeries/procedures

**Notes:**
The hospital use measures available from the NHDS include discharges; days of care, average length of stay, diagnoses, and surgeries or procedures.

## Discharges

- Include deaths
- Include transfers to other hospitals or long-term care facilities
- Do not usually include newborn infants

**Notes:**
The formal definition of a discharge is a completed inpatient hospitalization.   Hospitalizations are most often completed by releasing patients their usual place of residence.  But they can also be completed by death, or by transferring the patient to another short-stay or long-stay hospital, nursing home, or other long-term care facility.

Most estimates of discharges and other use statistics you will see in our publications exclude newborn infants.  But newborns are included in the survey and can be included in data you analyze, or they can be examined separately.

## Days of Care

- Total number of days discharged patients spend in the hospital
- All stays are counted as at least 1 day
- The admission day is counted, but not the discharge day
- The number of days divided by the number of discharges is the average length of stay

**Notes:**
Days of care are the total number of days discharged patients spent in the hospital.  All stays are counted as at least one day, even if the patients is present only for part of a day, for example if the patient is transferred to a different hospital after only a few hours of treatment.

For hospital stays of more than one day, the admission date is counted but the discharge day is not.

The average length of stay is the mean length of stay for discharged patients and is calculated by dividing the number of days of care by the number of discharges. 

## Diagnoses

- Disease, injury or other reason for hospitalization
- Coded according to US adaptations of the International Classification of Diseases (ICD-9-CM)

**Notes:**
A diagnosis is a disease or injury - or some other reason for going to the hospital, like to have cosmetic surgery or donate a kidney - that is listed on the patient’s medical record.  It is usually abstracted from the face sheet or discharge summary of the medical record.   We code diagnoses according the US adaptions of the International Classification of Diseases, which I’ll say more about later.

## Diagnoses

- Principal diagnosis: chiefly responsible for hospitalization
- First-listed diagnosis: principal if specified, otherwise one listed first

**Notes:**
There are several different ways you can count diagnoses with NHDS data.  The principal diagnosis is officially defined as “The diagnosis established after study to be chiefly responsible for the admission of the patient to the hospital.”  So if a patient is admitted complaining of chest pain and a chest x-ray shows pneumonia, the principal diagnosis at discharge would be pneumonia. 

However, the principal diagnosis is not always indicated on the medical record.  So we also have what we call the first-listed diagnosis.  This is the principal diagnosis if it’s listed, otherwise it’s the diagnosis listed first on the medical record. 

## Diagnoses

- All-listed: total number of times diagnoses appears on record
- Any-listed: discharges with diagnosis in any position on record

**Notes:**
In addition, we can estimate all-listed and any-listed diagnoses.  All-listed diagnoses are a count of the number of times a diagnosis appears on the medical record whether it is listed first or is one of the up to six secondary diagnosis that can be coded.  This measure is  often of interest for a diagnosis such as diabetes that complicates many other conditions.

Any-listed diagnoses are similar, a count of the number of discharges that have a certain diagnosis listed in any position, first-listed or secondary.  When a person can only have one of a condition, such as gall bladder disease, the any-listed number would be the same as the all-listed number.

## Hospital discharges with fractures, 2004

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

**Notes:**
However, as you can see in this example, when you use a large category, such as “fracture,” the number of times the diagnoses appears on the medical record can be larger than the number of people with the diagnosis.  A hospitalized patient can have a broken arm and a broken leg.  And neither of these may be the principal or first-listed diagnosis if, for example, the patient had a stroke that resulted in the fall and the broken bones. 

## Surgery / Procedures

- Surgical (appendectomy)
- Diagnostic (spinal tap)
- Therapeutic (chemotherapy) procedures
- Coded according to US adaptations of the International Classification of Diseases

**Notes:**
In addition to diagnoses, information on procedures is collected in the NHDS.  Procedures can be surgical, such as appendectomy, diagnostic, such as spinal tap, or  therapeutic, such as chemotherapy.  As many as  four procedures can be coded per discharge,  using the same coding system as the diagnostic data. 

We generally produce data on all-listed procedures, though any-listed estimates are also used in research, especially when the analyst wants to compute a death rate or average length of stay for discharges with a certain procedure.

## 
NHDS provides data on

inpatient procedures
 not total procedures

**NHDS provides**** data on**
*inpatient procedures*
-  not total procedures

**Notes:**
It is important to remember that the NHDS only provides data on inpatient procedures, not all procedures.  If you want to know how many hernia repair operations are being done in the US, you can not get the answer from the NHDS.  You can get a piece of the answer, but you would also need to find out the number being done in ambulatory surgery settings.

In 1994-1996, we were able to provide estimates on the total number of procedures performed in the United States, because we collected data on procedures being performed in ambulatory surgery settings via the National Survey of Ambulatory Surgery. The NSAS is being re-fielded in 2006, so we will again be able to produce estimates on the total number of procedures performed in the US. Bob will speak more about the NSAS later in this session. 

## Versions of the International Classification of Diseases

- 8th revision used 1970-78
- 9th revision used 1979-present
- 10th revision for use in future

**Notes:**
Over the years the NHDS has been in operation, we have used several different versions of the International Classification of Diseases.  From 1970 through 1978, we used the 8th revision, adapted for use in the United States.  And since 1979 we have used the 9th revision, clinical modification.  The 10th version has been used for mortality coding for several years, but we do not have a projected date for its use in the NHDS.

## ICD 8th Revision

- Some codes different than in 9th  Revision
- Did not use E-codes
- Made modifications in coding to accommodate available data

**Notes:**
The different versions of the ICD can have different code numbers for the same condition or procedure, which complicates trend analysis.
In addition, we did not use the E codes that indicate external cause of injury in the  8th revision.  And we made other changes in the coding system, deleting and combining certain codes.  Information about those modifications is available in the NHDS annual reports or file documentation for that time period. 

##  ICD 9th Revision

- Addenda added annually since 1986
- Codes added, deleted, expanded, and revised
- Lists of changes available in annual summary reports, file documentation

**Notes:**
When we began using the 9th revision of the ICD, WE no longer made modifications in the codes.  But beginning in 1986, addenda to the coding manuals have been released each year that modify certain codes.  Diagnostic and procedure codes have been deleted, expanded, revised, renamed.  These changes are outlined in what are called conversion tables, which are available online, in our annual summary reports and data file documentation.  For any research using coded data, it is important to check your codes in the conversion table to be sure they still mean what you think they mean.

## Weights

- Must use weighted data to obtain unbiased national estimates
- Each record has a weight
- Sum the weights of the records

**Notes:**
Turning to statistical issues, I want to remind you that if you want unbiased national estimates from the NHDS, you have to use the weighted data, not the number of records.  Using weighted data may sound very complicated, but it isn’t.  Each record has a weight, so instead of adding up the number of records in the category of interest, you sum the weights of the records.  A simple line of programming will take care of it.

## Reliability

- To be reliable, estimates must be based on at least 30 records
- And have a relative standard error of less than 30 percent
- Estimates based on 30-59 records should be used with caution

**Notes:**
As with any data from a sample survey, you have to take sampling error into account when you use the data.  Our guidelines for reliable estimates are that they should be based on at least 30 records, and they should have a relative standard error of less than 30 percent.  We also recommend that you use estimates based on 30-59 records with caution because of the clustering in our sample design.

## Standard Errors	

- Some standard errors are in Advance Data summaries
- Generalized error curves are in the Series 13 Annual Summaries and data documentation
- Use SUDAAN for specific standard errors - need access to confidential data

**Notes:**
One place to find standard errors is in the annual tables published in the Advance Data series.  Every estimate in those tables has its standard error next to it.  Of course, that will only help you if the estimate you want is included in the tables.  

For the ones that are not, you can compute relative standard errors from generalized error curves that are published in our Vital and Health Statistics Series Annual Summary reports and are provided in the data file documentation.  These curves are will allow you to calculate more standard errors.  

But we don’t have curves for all the variables or subcategories of variables  you might want to analyze.  And they don’t work for model-building procedures like logistic regression.  To calculate standard errors for specific estimates, you would need to use SUDAAN, which takes the complex design of the NHDS into account.  Marni will be telling you more about all that.

But first, Jean Kozak will share examples of research using NHDS data.

## Examples of Research

- Jean Kozak, Ph.D.

## Percent distribution of discharges and days of care by age, 2004

- Discharges

- Days of care

- 0-4

- 5-14

- 15-24

- 25-34

- 35-44

- 45-54

- 55-64

- 65-74

- 75-84

- 85 and over

- Age in years

- 10

- 10

- 0

- 20

- 20

- Percent distribution

**Percent distribution of discharges ****and days of care by age, 2004**

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

## Average length of hospital stay by age, 1980-2004

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

## Percent of hospital inpatients transferred to long-term care facilities, by age, 1990-2004

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

## Hospitalization rates for major diagnostic categories by sex, 2004

**Males**

**Females**

**Hospitalization rates for major diagnostic categories by sex, 2004**

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

## Percent distribution of patients hospitalized for heart disease, 2003

**Percent distribution of patients hospitalized for heart disease, 2003**

**All other diagnoses 87%**

## Hospitalization rate for cancer,1990-2004

**1990**
**63.0 **

**2004**
**41.2**

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

## Number of discharges with HIV diagnoses by age, 1995, 2000 and 2004

**Number of discharges with HIV diagnoses by age, 1995, 2000 and 2004**

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

## Hospitalization rates for depression for boys and girls 5-19 years of age, 1990-92 and 2002-04

**Hospitalization rates for depression for boys and girls 5-19 years of age,**** 1990-92 and 2002-04**

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

## Hospitalization rates for inpatients with Clostridium difficile by age, 1996-2003

**Hospitalization rates for inpatients with *****Clostridium difficile***** by age, ****1996-2003**

- Source: McDonald LC, et al. Emerg Infect Dis. 2006;12(3): 410-5.

**Black  patients**

**White patients**

**Hospitalization rates for avoidable conditions by race, patients under 65 years of age, 1990-2004**

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

## Average length of stay for selected diagnostic categories, 2004

**Average length of stay for selected diagnostic categories, 2004**

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

## Average length of stay for hip fractures, 1990-2004

**1990**

**6.4 days**

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

**12.8 days**

**2004**

**Average length of stay for hip fractures, 1990-2004**

## Length of hospitalization for childbirth, 1980-2004

**Length of hospitalization for childbirth, 1980-2004**

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

## Rate of cardiac catheterizations by sex, age, and geographic region, 2004

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

**Rate of cardiac catheterizations by sex, age, and geographic region, 2004**

## Coronary artery bypass grafts (CABGs) and percutaneous coronary interventions (PCIs),1980-2004

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

**Coronary artery bypass grafts (CABGs) and percutaneous coronary interventions (PCIs),1980-2004**

## Percent distribution of white and black discharges with coronary angioplasty according to stent use, 2003

**30.5%**

**22.0%**

**White patients**

**Black patients**

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

**Percent distribution of white and black discharges with coronary angioplasty according to stent use, 2003**

## Hospitalization rates for obese patients with gastric bypass, 1998-2003

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

**Hospitalization rates for obese patients with gastric bypass, ****1998-2003**

## Rate of cesarean delivery, 1970-2004

**1970**
**  ****5.5**

**2004**
**29.9**

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

**Rate of cesarean delivery, 1970-2004**

## Rate of vaginal birth after cesarean (VBAC), 1990-2004

**1990**
** ****20.4**

**2004**
**10.9**

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

**Rate of vaginal birth after cesarean (VBAC), 1990-2004**

## Rate of forceps and vacuum extraction, 1990-2004

**Forceps**

**Vacuum**

- Source:  CDC/NCHS, National Hospital Discharge Survey (NHDS)

**Rate of forceps and vacuum extraction, 1990-2004**

## Data users

- Hospitals
- Universities and medical schools
- Professional organizations, such as AMA, AHA, WHO
- Government agencies, such as NIH, CMS, CDC, IHS
- Medical research organizations, pharmaceutical and medical supply manufacturers, insurance companies
- News media
- Other users such as publishing houses, market research groups, free lance writers

## Accessing Data from the National Hospital Discharge Survey

- Marni Hall, Ph.D.

**Notes:**
Good Afternoon.  I’m Marni Hall and I am going to give you some general guidance on how to access the National Hospital Discharge Survey data. I’ll begin by outlining the types of data that are available, and then I’ll discuss how to get the data you want.

BUT FIRST, I WANT TO EMPHASIZE THAT YOU DO NOT NEED TO TRY TO COPY THE VARIOUS WEBSITES I WILL SHOW YOU ON THESE SLIDES.  EVERYTHING THAT I HAVE HERE IS INCLUDED IN THE INTERNET RESOURCES HANDOUT THAT IS AVAILABLE ON THE TABLE IN THE BACK OF THE ROOM.  ALSO, THESE AND MY COLLEAGUES’ SLIDES ARE AVAILABLE IN THE HANDOUT ON THE BACK TABLE AS WELL. 

## How can you get the data?

- In publications, including annual reports
- From data tabulations on selected topics
- Using public-use data files (micro-data)
- Calling NCHS to request tabulations

**Notes:**
You can get the data you need from a number of different sources depending upon the type and amount of data you need.  If you just need one or more national estimates, e.g. the estimated number of hospitalizations for asthma in a given year you can find that in our annual publications or can call or email us.  For more extensive information, like the number and rate of cardiovascular procedures performed on the elderly over the past 10 years, you may be better off downloading the public use files and analyzing the data yourself.

Each year we produce two reports and generate a number of tabulations which provide literally hundreds of statistics commonly requested by consumers of the Hospital Discharge Survey data.  We also release a public use data file annually, which contains the microdata or discharge level information collected in the survey.

## On the NHDS/NSAS homepage www.cdc.gov/nchs/about/major/hdasd/nhds.htm

- You’ll find:
- A Description and Methodology of NHDS (and NSAS)
- Downloadable Publications from NCHS
- List of other publications using NHDS or NSAS data
- Public Use Files – micro data

**Notes:**
The answers to many of the requests for data we get can be answered by going to the Hospital Discharge and Ambulatory Surgery website.  Here you will find the information listed on this slide – a description and the methodology for the surveys, our NHDS publications, lists of other articles which use our data, and the public use data files.

## How to get to the NHDS/NSAS webpage from the NCHS homepage

- _[www.cdc.gov/nchs](http://www.cdc.gov/nchs)_
- Under Surveys & Data Collection Systems on the far left of the screen
- Select NHCS which stands for National Health Care Survey
- When a pop-up list of surveys appears, select **National Hospital Discharge Survey**

**Notes:**
On the internet you should begin at the NCHS homepage at www.cdc.gov/nchs. On the left hand side of this screen you will see a section with a dark blue background.  Most of what I will tell you about in the remainder of this presentation can be found under the categories you see listed there.  First go down to the section called Surveys and Data Collection Systems.  A popup menu will appear which lists various surveys and you should select the National Health Care Survey.  Then another list will appear of the component surveys in the National Health Care Survey.  You can choose the National Hospital Discharge Survey.  This will lead you to the homepage for the NHDS and NSAS.  

## Slide 64

## Annual Publications using NHDS

- Advance Data reports
- 2004 available on the website
- Annual Summary with Detailed Diagnosis and Procedure Data
- 2003 available on the website
- 2004 available later this summer

**Notes:**
The two basic publications which we produce each year are the ADVANCE DATA and the SERIES 13, VITAL AND HEALTH STATISTICS REPORT, which we call the ANNUAL SUMMARY.  
The AD provides an early release of the NHDS data and is quite short and very general.  The latest available under the publications section of our homepage is the 2004 AD.
The ANNUAL SUMMARY  is more comprehensive than the AD in that it provides data on a number of timely and interesting topics as well as DETAILED DIAGNOSES AND PROCEDURES tables. For those not familiar with the detailed tables, they contain estimates for every ICD-9-CM diagnosis and procedure code for which we have reliable data.  I’ll tell you where to get the codes for the diagnoses and procedures if you don’t know them a little later in this presentation.  

The latest version of the Annual Summary on the website now is 2003 but the 2004 will be available later this summer.

## How to download publications

- Publications, data tables, and data file documentation are in Adobe Acrobat PDF format
- Require use of the free Adobe Acrobat Reader software, available for download at: _[www.adobe.com](http://www.adobe.com/)_

**Notes:**
The publications, data tables, and data file documentation are provided in Adobe Acrobat format.  The Adobe Acrobat Reader software can be downloaded for free from the website given here.  

## Public-Use Files Available on the Web

- Data files and documentation available for free from the NHDS webpage
- NHDS: 1996 through 2004
- NSAS: 1994, 1995, 1996*
- 		*2006 NSAS data will be available early in 2008

**Notes:**
For the NHDS, data files and documentation are available for the 1996 through 2004 data years. I’ve also listed the NSAS data files here.  The NSAS data being gathered now and throughout 2006 is expected to be available early in 2008. 

## Obtaining and using data files

- Data files are in ASCII format and must be downloaded via FTP server.
- Downloadable public-use data files are “zipped” for a speedier download
- “Unzip” these files with free data extraction software such as:
- WinZip (_[www.winzip.com](http://www.winzip.com/)_)
- PKunzip (_[www.pkware.com](http://www.pkware.com/)_)

**Notes:**
Microdata files are in ASCII format and must be downloaded through the FTP server.  To speed the download the files are zipped, which means they must be unzipped after downloading.  The location of free software to unzip the files is noted here.

## Analyzing Public Use Data

- Files require the use of standard statistical software packages, such as SAS, SPSS, Stata, etc.

**Notes:**
These ASCII or text data files must be analyzed with SAS, SPSS, STATA, or other types of standard statistical software.  They are very large files, about 300,000 records, so are too big for EXCEL to handle.

As I mentioned previously the documentation to accompany the data files is also downloadable, and is provided in PDF format.

## Multi-year data files

- Two separate multi-year files on CD-ROM are available for free from NCHS:
- 	 1970-1978 data years (ICD-8 coding)
- 1979-2004 data years (ICD-9-CM coding)
- DRG’s are not included on the multi-year files.
- For NSAS a 1994-1996 data file is available.

**Notes:**
We have two separate multi-year NHDS data files available on CD-ROM for free.  The first one is for 1970 to 1978 and the second is for 1979 to 2004.  One catuionary note – if you are interested in running these data by DRG’s you have to get files for the individual years because DRG’s are not on the multi-year files. For NSAS we have a data file with data from the three years that were gathered: 1994, 1995, and 1996.

## Where to find ICD-9-CM codes for Diagnoses or Procedures

- _[www.cdc.gov/nchs/icd9.htm](http://www.cdc.gov/nchs/icd9.htm)__ _
- Full-text ICD-9-CM documents are RTF (Rich Text Format) files and can be handled with any word processing package
- Addenda and conversion tables are PDF documents
- Very lengthy document

**Notes:**
As has been mentioned, our medical diagnosis and procedure data is coded using the ICD-9-CM.  Here is a website where you can find this coding system, as well as the addenda and conversion tables, showing changes in codes over time. You probably do not want to download the full-text of the coding book, as it is a very large document.  You can also get to this classification system from the NCHS homepage by scrolling down the dark blue area on the right side to Disease Classification under Inititatives.

## Publications and Information Products 

- _[http://www.cdc.gov/nchs/products.htm](http://www.cdc.gov/nchs/products.htm)_
- Lists electronic products
- Additional Information about obtaining reports, data, and other products

**Notes:**
Also from the NCHS homepage you can click on Publications and Information Products to find out information about  earlier reports and data that are available.  That is, I have already mentioned that you can get recent reports on the hospital discharge survey website but this is how you find older reports.  If you have any trouble finding out how to order something that you want, please call or email us.

## Other sources of tabulated NHDS Data

- FASTATS A to Z
- Aging – Trends in Aging Database provides information on national trends and key variables that depict the health status of older Americans compiled from a number of surveys – mostly on persons 50 years old and over
- Healthy People
- Health, United States

**Notes:**
Here are some other sites that you can get to from the NCHS homepage which have data not only from the NHDS but from other surveys.  FASTATS is an alphabetical list of health topics which present some basic statistics, and the source of the data.  

Under Trends in Aging also under Initiatives is  a database with information primarily on people 50 years and older.

Healthy People is also a topic in the dark blue area and this includes departmental health goals which are tracked over time using NHDS and other data sources.

And Health United States is also mentioned on the homepage but over in the second column.  This annual report to Congress includes a wealth of health data including NHDS. Surveys of the NCHS and other data sources. 

## Restricted Data in NHDS

- _[http://www.cdc.gov/nchs/r&d/rdc.htm](http://www.cdc.gov/nchs/r&d/rdc.htm)_
- HCSB maintains confidential information in files which are not publicly disseminated
- Restricted data pose disclosure risks to survey respondents
- These data are available to researchers through the NCHS Research Data Center (RDC)

**Notes:**
I just want to spend a couple of minutes talking about data from the NHDS that is not publicly released, but can be accessed through the NCHS Research Data Center.  Restrictions are placed on this data because they pose possible disclosure risks to survey respondents, who are promised that their identity will be kept confidential.

These files are available only with prior approval through the NCHS Research Data Center.  To find out what procedures you need to follow to use the RDC, you can go the website shown here.  In addition to  submitting a proposal for NCHS approval, researchers pay a fee for using the RDC.  

## Confidential files for NHDS and NSAS variance estimation
NHDS and NSAS analytic files that have been linked with outside data sources

- NHDS and NSAS analytic files that have been linked with outside data sources

**Through the RDC ****Researchers Can Use:**

**Notes:**
The files that are available in the RDC contain information needed for variance estimation for both NHDS and NSAS, as well as key variables that can serve as links to outside data sources, that can be merged with the NHDS to augment its analytical capability.

## ZIP Codes for residence of patient and for hospitals
State/County FIPS CODE for both patient and hospital
AHA ID for hospital
Design Variables needed to run SUDAAN
NOTE:  Identifiers such as patient name, address, and SSN are not collected in the NHDS

- State/County FIPS CODE for both patient and hospital
- AHA ID for hospital
- Design Variables needed to run SUDAAN
**NOTE**:  Identifiers such as patient name, address, and SSN are not collected in the NHDS

**Confidential Variables Available ****only on Restricted Files**

**Notes:**
Variables that can be used to link NHDS with other data sources include the ZIPCODE for the patient’s residence and for the hospital, STATE/COUNTY FIPS CODES for both patient and hospital, and AHA ID for the hospital.  Also available on confidential files are design variables needed to run SUDAAN.  

Patient name, address, and medical record number are not collected in the NHDS, so they can not be used for linkage to other files.

## NHDS Can be Linked with Other Files, for example

- American Hospital Association File (AHA) which has data on hospital characteristics
- Area Resource File (ARF) which has county level data (e.g. SES variables and health service availability)
- Linkage is with contextual NOT personal / demographic information

**Notes:**
The NHDS has been linked with the American Hospital Association database and the Area Resource File.  This linkage augments the NHDS file with contextual information about hospitals or counties where patients live or hospitals are located.  It does not provide any additional personal or demographic information for the patients themselves.  Contextual data include characteristics of the hospitals and county-level socio-economic, health care utilization, and vital statistics information.

## NHDS or NSAS Questions?

- By telephone:
- Hospital Care Statistics Branch:  301-458-4321
- NCHS Information Dissemination Staff  (toll free)    1-866-441-NCHS  [1-866-441-6247]
- Send an email to:  _[NHDS@cdc.gov](mailto:NHDS@cdc.gov)__ _

**Notes:**
Here is our phone number, FAX, and email address, so feel free to contact us if you have questions. 

Thank you for your attention.  Bob Pokras will now provide the final presentation of this session.

## Future Activities and Directions

- Robert Pokras, MA

## Future Activities and Directions

- Redesigning the NHDS
- Refielding the NSAS

## Context for Redesigning the NHDS

- Data elements limited to UB 92 (UB 04)
- The value of primary data collection to meeting current and future policy and research needs
- To take a fresh look at current and future policy and research issues and associated data needs and gaps
- Meetings and interviews
- Working group meeting in March, 2006

## Priority Issues

**Cost of care/ use of resources**
- including efficiency/ waste
**Quality of care/ safety**
- including disparities
**Care delivered in the hospital**
**Surveillance and public health**
- including surge capacity
**Globalization**
- including outsourcing

## Coordinate with AHRQ data collection (HCUP)
Add resource use/ cost/ billings/ payments
Add clinical depth
e.g., medications, tests
Improve patient demographics
e.g., ethnicity
Link to health-related outcomes
e.g., death index

**Add resource use/ cost**/ billings/ payments
**Add clinical depth**
- e.g., medications, tests
**Improve patient demographics**
- e.g., ethnicity
**Link to health-related outcomes**
- e.g., death index

**Highest Rated Options for Redesign**

## Clinical Depth Core Data Set(All Sampled Cases)

- Height
- Weight
- Administered drugs

## Clinical DepthDiagnostic/ Procedure/ DemographicModule (Subsample of Cases)

- Lab values
- Pathology results

## Resource Use/ Cost/ Efficiency

- Billings -- charges
- Medicare program
- Cost-to-charge ratios
- DRG hospital-specific payments

## Improved Patient Demographics

- Race
- Ethnicity

## Link to Health-Related Outcomes

- Link with the National Death Index to look at 30-day mortality

## Additional Aspects of the Redesign

- Link mother and newborn records
- Collect data from ED and observation status (for sampled inpatients)
- Collect data from last previous admission
- Length of stay
- Principal diagnosis

## Summer 2006:
 Final conceptual framework
 Strategy and data elements
2006-2007: Feasibility test in 9 hospitals
2007: Contract for field test
2008: Field test
2010: New survey fielded

-  Final conceptual framework
-  Strategy and data elements
- 2006-2007: Feasibility test in 9 hospitals
- 2007: Contract for field test
- 2008: Field test
- 2010: New survey fielded

**Next Steps**

## Refielding the National Survey of Ambulatory Surgery (NSAS)

- First fielded in 1994-1996
- Back in the field for 2006
- Data collect ends in March 2007
- Public Use files will be available in early 2008

## Breast lumpectomy procedures

**Ambulatory**

**Inpatient**

**Total**

- ?

- Sources:  CDC/NCHS, National Survey of Ambulatory Surgery (NSAS) and National Hospital Discharge Survey (NHDS)

**Breast lumpectomy procedures**

**.**

**.**

**.**

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## Any questions?