# Presentation: 490590

## National Hospital Discharge Survey(NHDS)

- National Survey of Ambulatory Surgery
- (NSAS)

_**Centers for Disease Control and Prevention**_

## Session Overview

- NHDS and NSAS:  Overview
- Bob Pokras
- Analytic Issues
- Jean Kozak, Ph.D.
- Examples of Research
- Marni Hall, Ph.D.
- Accessing Data
- Maria Owings, Ph.D.
- New Directions

## Slide 3

## National Health Care Surveys

- Visits to
- Doctors’ offices (NAMCS)
- Emergency rooms (NHAMCS)
- Outpatient departments (NHAMCS)
**Inpatients (NHDS)**
**Ambulatory surgery (NSAS) (1994-96)**
- Long term care
- Nursing homes (NNHS)
- Home health care (NHHCS)
- Hospices (NHHCS)

## Handout

- Internet Resources:  Hospital Discharge and Ambulatory Surgery Data
- For an email of this table of hotlinks, write to:  _[NHDS@cdc.gov](mailto:NHDS@cdc.gov)_

## Slide 6

## Slide 7

## Survey Years

- NHDS:  Annually 1965-present
- Latest data available – 2000
- 2001 will be available this Winter
- NSAS:  Annually 1994-1996

## Survey Design and Operations

- NCHS Publications
- NSAS – Series 1 No. 37
- NHDS – Series 1 No. 39

## Slide 10

## Slide 11

## Survey Design

- Similar designs and methods
- National probability samples
- Short stay non-Federal hospitals (NHDS/NSAS)
- Freestanding ambulatory surgery centers (NSAS)

## Survey Design

- Three stage design
- PSU
- Facility
- Discharge/visit

## Facility Sample Size

- 525 NHDS hospitals
- 751 NSAS facilities
- 418 Hospitals
- 333 Freestanding surgery centers

## Response Rates

- NHDS – over 90 percent
-   300,000 sampled discharges per year
- NSAS -- 80 percent for hospitals
-             -- 70 percent for FSASC
-   120,000 sampled visits per year

## Data Collection

- NHDS
- Manual; 60%
- Automated; 40%
- NSAS
- All manual

## Manual Data Collection

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

## Automated Data Collection

- Purchase files
- States
- Commercial firms
- Individual hospitals

## Data Collection

- NCHS
- Editing
- Estimation

## Estimation

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

## Variables on Public Use Data Files

## Slide 22

## Slide 23

## Patient Data

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

## Facility Characteristics

- Geographic region
- Bed size (NHDS)
- Ownership (NHDS)
- Hospital vs. Freestanding (NSAS)

## Medical Data

- Diagnoses and procedures
- International Classification of Diseases, 9th Revision, Clinical Modification             (ICD-9-CM)

## Additional Variables

- NHDS
- Days of care
- Month of admission/discharge
- DRG
- NSAS
- Month of visit
- Type of anesthesia
- Anesthesia provider
- WEIGHT

## New Variables for NHDS

- Available for Year 2001 NHDS
- Source of Admission
- Type of Admission

## Source of Admission

- Physician Referral
- Clinical Referral
- HMO Referral
- Transfer from a Hospital
- Transfer from Skilled Nursing Facility
- Transfer from other health facility
- Emergency Room
- Court/Law Enforcement
- Other
- Not Available

## Type of Admission

- Emergent
- Urgent
- Elective
- Newborn
- Not available/unknown

## Slide 31

## Summary

- Source of the data
- Design
- Methods
- Variables

## Analytic Issues(things  you need to know about NHDS data) 

- <date/time>

- Analytic Issues(things  you need to know about NHDS data)

-  Lola Jean Kozak, Ph.D.

##    Topics

- Utilization measures
- Populations
- Medical coding system
- Statistical issues

## NHDS Provides Data on

- <date/time>

- NHDS Provides Data on

- Hospitalizations
-  Not People

##    Measures Include:

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

## Discharges

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

## 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

## Average Length of Stay

- Calculated by dividing the number of days of care by the number of discharges
- May want to examine length of stay distributions

## Length of stay for women with deliveries:  1995 and 2000

- Discharges in thousands

## Diagnoses	

- Disease, injury or other reason for hospitalization
- Coded according to US adaptations of the International Classification of Diseases

## Diagnoses	

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

## Diagnoses	

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

## Hospital discharges with fractures, 2000

- Principal or first listed

- Any listed

- All listed

- 982,000

- 1,226,000

- 1,542,000

##  Surgery/Procedures

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

## NHDS Provides Data on

- <date/time>

- NHDS Provides Data on

- Inpatient Procedures
-  Not Total Procedures

## Procedures mainly performed in inpatient settings, 1996

- Cesarean
- section

- Hysterectomy

- Coronary artery bypass graft

- Appendectomy

- Number in thousands

## Procedures mainly performed in ambulatory settings, 1996

- Insertion
- of lens

- Endoscopy of
- large intestine

- D & C

- Arthroscopy
- Of knee

- Number in thousands

##  Population for Rates 

- Mid-year population estimates from the U.S. Bureau of the Census
- Civilian resident population
- Adjustments for underenumeration

## Versions of the International Classification of Diseases

- 8th revision used 1970-78
- 9th revision used 1979-2002
- 10th revision for use in future

##  8th Revision

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

##  9th Revision

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

## Weights	

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

## Reliable Estimates

- Are based on 30 records or more*
- And have a relative standard error of 30 percent or less
- *Use estimates based on 30-59 records with caution

## 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

## Examples of Research Using the National Hospital Discharge Survey

- Marni Hall, Ph.D.

## Hospital Transfers to Long Term Care Facilities in the 1990’s

- Lola Jean Kozak, Ph.D.
- Long-Term Care Interface – June 2002

## Transfers to long-term care,1990-1999

- Number in Millions

- 1.6 Million

- 2.8 Million

## Average hospital stay for long-term transfers, 1990-1999

- 12.8 days

- 8.3 days

## Hospital discharges transferred to long-term care institutions by length of stay, 1990-1999

- Hospital Stay

- Transfers in Thousands

## Long-term transfers by first-listed diagnoses

- 0

- 100

- 300

- 600

- 600

- 300

- 100

- 1990

- 1999

**Circulatory**

**Respiratory**

**Injury & poisoning**

**Digestive**

**Musculoskeletal**

**Endocrine,  metabolic **

**Genitourinary**

**Neoplasms**

**Infectious & parasitic**

**Mental disorders**

- Number in thousands

##  Hospital Transfers to Long Term Care Institutions study:

- Trend data – 10 years
- Changing roles of hospitals and nursing homes
- Assessment of the effects of Medicare policy changes
- Post-acute care in nursing homes substituting for end of hospital stay

## Trends in Avoidable Hospitalization: United States, 1980-1998

- Lola Jean Kozak, Ph.D.
- Margaret J. Hall, Ph.D.
- and Maria F. Owings Ph.D.

## Avoidable hospitalization diagnoses

- Selected by a panel of physicians
- Can often be prevented, controlled, or managed over time without the need for hospitalization if the patient receives timely and  appropriate ambulatory care
- Used as indicators of access and the adequacy of ambulatory care

## Diagnoses studied in avoidable hospitalization study

- Pneumonia
- Congestive heart failure
- Asthma
- Cellulitis
- Perforated or bleeding ulcer
- Pyelonephritis
- Diabetes with ketoacidosis or coma
- Ruptured appendix
- Malignant hypertension
- Hypokalemia
- Immunizable conditions
- Gangrene

## Avoidable hospitalizations	

-                                   1980		1998**  **
-  #  of discharges    2,200,000	3,700,000 million
- Rate per 1,000
-     population		 99.2		133.8

## Trend in rate of avoidable hospitalizations 

- 99.2

- 133.8

## Trend in rate of other hospitalizations 

- 157.8

- 103.1

## Trend in rate of avoidable hospitalizations

- Under 65

- Over 65

- 364.6

- 573.5

- 65

- 71.1

## Trend in rate of avoidable hospitalizations for those over 65

- Whites

- Blacks

- 352.8

- 564

- 325.2

- 450

## Trend in rate of avoidable hospitalizations for those under 65

- Blacks

- Whites

- 92.5

- 113.5

- 53.8

- 49.1

## Avoidable hospitalization study:

- Trend data – 20 years
- Avoidable hospitalization conditions as defined by the literature
- Measured access to care over time
- Identified disparities between elderly/nonelderly and white/black and identified those who should be targeted for intervention
- Used as a model for additional research funded by Center for Medicare and Medicaid Services

## Pneumonia hospital discharge rate for the elderly

**Rate per 10,000**

- 65 and over

- 125.3

- 221.2

## Disparities in the Rate of Hospitalization for Pneumonia  Patients in Rural and Urban Areas

- Maria F. Owings, Ph.D.
- Margaret J. Hall, Ph.D.

## Study Objectives

- To compare urban and rural patients hospitalized for pneumonia based on
- Patient characteristics
- County characteristics, including health services availability and socioeconomic status (SES)

## Disparity in Urban/Rural Pneumonia Hospitalizations, 2000

**37.5**

**78.0**

**Rate per 10,000 population**

- Rural

- Urban

## Indicators of Severity of Illness

-                              	Urban		Rural
- Average # diagnoses     		5.1		 4.9
- % with serious
-     comorbidities 		36%		 40%
- Average # seriouscomorbidities 		1.2		 1.3**1**
**1**Significant Difference

## 				
		Urban	Rural
Average age  	 	59		641

Average length of 		6.2            		5.31stay (days) 		

Routine Discharge	  	70%		65%

1Significant difference 

- 		Urban	Rural
- Average age  	 	59		64**1**
- Average length of 		6.2            		5.3**1**stay (days)
- Routine Discharge	  	70%		65%
**1**Significant difference

- Indicators of Severity of Illness

## Education, Unemployment 

** **

**            **

-  **% w/some college**

**Unemployment rate**

- Education, Unemployment
- and Poverty

**% in poverty**

## MD/Hospital Availability

** **

**            **

**Active MD’s**

**Hospital Beds**

**Rate per  1,000 elderly**

## Rate per 1,000 elderly

**Rate per 1,000 elderly**

## What policies could reduce avoidable hospitalizations?

- _Promotion of __rural__ managed care_
- Programs which _attract/keep __rural__ MD’s _
- More _affordable, accessible outpatient health care_
- _More health education / outreach programs_ - e.g. smoking cessation,  influenza / pneumonia shots

## Urban/rural pneumonia hospitalization study:

- Urban/rural indicators
- NHDS  merged with Area Resource File (ARF) data
- Severity of illness indicators using NHDS data
- Policy recommendations

## Medical Care Expenditures for Hypertension, Its Complications, and Its Comorbidities

- Thomas A. Hodgson, Ph.D. , NCHS
- Liming Cai, Ph.D., NOVA Research Co.

## Estimated the economic burden of hypertension using utilization for:

- First-listed hypertension
- Cardiovascular complications
- Unrelated conditions for which hypertensives are at greater risk
- Comorbidities, i.e. secondary diagnoses

## Data from the Centers for Medicare and Medicaid Services (CMS):

- Personal Health Expenditures
- Part B Data
- Data from the Agency for Healthcare Research and Quality (AHRQ):
- National Medical Expenditure Survey

## Data from the National Center for Health Statistics:

- National Hospital Discharge Survey
- National Ambulatory Medical Care Survey
- National Hospital Ambulatory Medical Care Survey
- National Home and Hospice Care Survey
- National Nursing Home Survey
- National Health Interview Survey

## Data on hospital costs were calculated using these data:

- National Hospital Discharge Survey data on the number of inpatient days
- National Medical Expenditure Survey data on the average facility charge per hospital inpatient day

## Total hospital expenditures attributed to hypertension

- $ 17.1 billion  - cardiovascular complications
- $ 24.2 billion  - other diagnoses
- ___________________________________
- $45.5 billion – total hospital expenditures 			      attributed to hypertension

## Expenditures for hypertension, 1998

- Hospital care
-         42%

- Physician Services
-             26%

- Prescription Drugs
-             17%

- Nursing home
-          12%

- Home health care
-  4%

## $ 22.8 billion  - diagnosis of hypertension	
$ 29.7 billion  - cardiovascular complications
$ 56.4 billion  - other diagnoses
___________________________________
$108.8 billion - total expenditures attributed 			        to hypertension  

- $ 29.7 billion  - cardiovascular complications
- $ 56.4 billion  - other diagnoses
- ___________________________________
- $108.8 billion - total expenditures attributed 			        to hypertension

- Total expenditures attributed to hypertension

## Expenditures for hypertension study:

- Example of how cost data can be combined with utilization data
- Hospital care studied as part of entire spectrum of health services – how it fits into the total picture
- Uses multiple national data sources
- Regression analyses
- Provides data for cost benefit analysis

## For more information see our Internet Resources handout

## Accessing Data from NHDS and NSAS

- Maria Owings, Ph.D.

_**Centers for Disease Control and Prevention**_

## Sources of Available Data

- Publications, including annual reports
- Downloadable from the Internet
- Data years 1985 through 2000
- Order and purchase – years before 1993
- Data tables on selected topics –viewed or downloaded from Internet
- Public-use data files for DO-IT-YOURSELF analysis
- Downloadable from the Internet
- On CD-ROM
- ICD-9-CM – to assist in using medical data

## Quick and Easy Access to NHDS and NSAS Data

- Telephone the Hospital Care Statistics Branch:  301-458-4321
- Send an email to:  _[NHDS@cdc.gov](mailto:NHDS@cdc.gov)_
- Go to the NCHS website on the World Wide Web: _[www.cdc.gov/nchs](http://www.cdc.gov/nchs)_

## Annual Publications

- ADVANCE DATA on Vital and Health Statistics reports provide early release of NHDS data
- Very general and usually short
- Series 13 Reports provide more specific statistics on hospital utilization
- Are more comprehensive and contain detailed tables of diagnoses and procedures

## Recent Annual Publications

- 2000 NHDS Advance Data : _[http://www.cdc.gov/nchs/data/ad/ad329.pdf](http://www.cdc.gov/nchs/data/ad/ad329.pdf)__ _
- 1999 NHDS Annual Summary : _[http://www.cdc.gov/nchs/data/series/sr_13/sr13_151.pdf](http://www.cdc.gov/nchs/data/series/sr_13/sr13_151.pdf)__ _
- Includes estimates of diagnoses and procedures by detailed ICD-9-CM code number

## What to Know to Access Data and Pubs on the WWW

- Publications and data tables 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/)_

## Where to Find NHDS and NSAS Data and Pubs on the WWW

- 	_[http://www.cdc.gov/](http://www.cdc.gov/nchs/about/major/hdasd/listpubs.htm)__[nchs](http://www.cdc.gov/nchs/about/major/hdasd/listpubs.htm)__[/about/major/](http://www.cdc.gov/nchs/about/major/hdasd/listpubs.htm)__[hdasd](http://www.cdc.gov/nchs/about/major/hdasd/listpubs.htm)__[/](http://www.cdc.gov/nchs/about/major/hdasd/listpubs.htm)__[listpubs](http://www.cdc.gov/nchs/about/major/hdasd/listpubs.htm)__[.](http://www.cdc.gov/nchs/about/major/hdasd/listpubs.htm)__[htm ](http://www.cdc.gov/nchs/about/major/hdasd/listpubs.htm)_
- Lists annual pubs (back to 1990 only) and special topic reports by name and number
- 	_[http://www.cdc.gov/](http://www.cdc.gov/nchs/products.htm)__[nchs](http://www.cdc.gov/nchs/products.htm)__[/products.](http://www.cdc.gov/nchs/products.htm)__[htm ](http://www.cdc.gov/nchs/products.htm)_
- Provides links by topic area for all NCHS products (not just NHDS & NSAS), including
- Data Warehouse (for microdata and tabulations)
- Published Reports (by type, e.g. Advance Data, Series 13 Vital and Health Statistics, etc)
- 	--ADs and Series 13 for pre-1990 years

## NHDS & NSAS Homepage

- _[http://www.cdc.gov/nchs/about/major/hdasd/nhds.htm](http://www.cdc.gov/nchs/about/major/hdasd/nhds.htm)_ provides links to all aspects of survey design, data, and dissemination, including
- Survey Methodology and Data Collection
- Publications and Journal Articles
- Public Use Data Files (microdata)
- Special Reports
- NCHS Health E-Stats
- Data Highlights & Selected Tables on topics such as hospital discharges among females with deliveries, HIV inpatients, newborn infants, and hospital inpatient deaths, and ambulatory surgery utilization

## Public-Use Files Available on the Internet

- Data and documentation available for free from the NCHS website
- NHDS:   1996 through 2000
- NSAS:    1994, 1995, 1996
- These are “raw” ASCII  data that require the use of statistical software packages, such as SAS, SPSS, Stata, etc.

## What to Know to Access Public-Use Files on the WWW

- Downloadable public-use data files are “zipped” for a speedier download.
- “Unzip” these files with
- WinZip at _[http://www.](http://www.winzip.com/)__[winzip](http://www.winzip.com/)__[.com/](http://www.winzip.com/)_
-  PKunzip** at **_**[http://www.pkware.com/](http://www.pkware.com/)**_
- Data documentation are available either as text files or PDF files.

## Public-Use Files Available onCD-ROM

- Two separate multi-year files containing
- 1979-2000 data years (ICD-9-CM coding)
- 1970-1978 data years (ICD-8 coding)
- Single year files for 1990, 1994 to 2000
- IMPORTANT:   DRGs are available on single year files only.  Multi-year files do NOT have DRGs.

## How to Get PU Files on CD-ROM

- Can be obtained at no cost from NCHS
- Division of Data Services: 301-458-INFO
- Hospital Care Statistics Branch: 301-458-4321
- Or ordered from National Technical Information Service (NTIS)
-  by phone at 1-800-553-6847 or (703) 605-6000
-  online at  _[http://www.](http://www.ntis.gov/)__[ntis](http://www.ntis.gov/)__[.](http://www.ntis.gov/)__[gov](http://www.ntis.gov/)__[/](http://www.ntis.gov/)_
- Annual files for single years prior to 1994 can be ordered from NTIS, not directly from NCHS

## ICD-9-CM

- For full-text, addenda, and conversion tables of ICD-9-CM, see _[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.

## Restricted Data in NHDS 

- HCSB maintains confidential information in files which are restricted from unauthorized use
- These data are available to researchers through the NCHS Research Data Center (RDC)
- _[http://www.cdc.gov/nchs/r&d/rdc.htm](http://www.cdc.gov/nchs/r&d/rdc.htm)_

## Through the RDCResearchers Can Use:

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

## NCHS Research Data Center	

- Located within NCHS facilities in Hyattsville, MD
- Requires preapproval of research projects by an internal proposal review committee
- Subjects analytic results to disclosure limitation review and clearance
- Provides different modes of data access for approved research projects

## Confidential Variables Available Only on Restricted Files

- ZIPCODE for residence of discharged patient
- ZIPCODE for hospital
- STATE/COUNTY FIPS CODE for both patient and hospital
- AHA ID for hospital
- DESIGN VARIABLES needed to run SUDAAN to obtain variances of complex NHDS statistics
- 	********************************************
- NOTE:  Patient name and address are NOT collected in the NHDS

## Restricted Data Needed by SUDAAN for NHDS and NSAS Applications:

- Variables corresponding to design stages for sampling and stratification
- Population counts at each sampling stage
- Type of sampling performed at each stage

## SUDAAN Software

- Incorporates design-related variables unique to each survey
- Utilizes sampling weights of discharges and visits that reflect unequal probabilities of selection
- Produces sampling errors for NHDS and NSAS estimates that take into account the complexity of the survey design

## NHDS Linked Files

- NHDS + American Hospital Association (AHA)
- NHDS + Area Resource File (ARF)
- Linkage is with contextual NOT personal / demographic information
- Contextual data include
- Hospital characteristics, services (AHA)
- County level information (ARF)

## American Hospital Association (AHA) Database

- Hospital-specific data on over 6,200 hospitals and health care systems
- More than 600 data items collected with the assistance of State and Metropolitan Hospital Associations** **

## Types of Variables in AHA

- Organizational Structure
- Staffing
- Utilization
- Facilities and Services
- Financial
- Geographic codes
- Approval and Accreditation Codes

## Area Resource File(ARF)

- County-specific health resources information system designed to aid research on the health care delivery system and factors that may impact health status and health care in the U.S.
- Contains more than 7,000 variables from over 50 different source files for each county.

## General Categories of Variables in the ARF

- Health facilities
- Health professions
- Health care utilization
- Morbidity and mortality measures
- County economic activity
- Socioeconomic and environmental variables

## Beyond 20/20 Browser

- _[http://www.cdc.gov/nchs/about/otheract/aging/howto.htm#browser2](http://www.cdc.gov/nchs/about/otheract/aging/howto.htm#browser2)_
- Database providing up-to-date information on national trends and key variables that depict the health status of older Americans
- Data for persons 45 years old and over by sex and race

## Listserv

-  _[http://www.cdc.gov/nchs/about/major/hdasd/nhdslistserv.htm](http://www.cdc.gov/nchs/about/major/hdasd/nhdslistserv.htm)_
- Provides current information about new data releases and publications
- Subscribers can post messages to other members and exchange information

## How to Subscribe to HDAS Listserv

** **In the body of an email message           (leaving the subject line blank),  type:
-  subscribe hdas-data *your name*
-  Send this message to:
-  listserv@cdc.gov

## NHDS or NSAS Questions?

- Phone: 301-458-4321
- Fax: 301-458-4032
- Email: _[NHDS@cdc.gov](mailto:NHDS@cdc.gov)_

## New Directions

- Beyond 20/20
- Public use variance file

## New Directions

- Clinical data
- Evaluation of drugs in the NHDS
- Two phase contract
- Phase I – Research
- Phase II – Field test