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National Hospital Discharge Survey (NHDS) Session Overview NHDS: Overview Carol DeFrances, Ph.D. Analytic Issues Jean Kozak, Ph.D. Examples of Research Marni Hall, Ph.D. Accessing Data Maria Owings, Ph.D. New Directions Bob Pokras

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Session overview l.jpg

Session Overview

NHDS: Overview

Carol DeFrances, Ph.D.

Analytic Issues

Jean Kozak, Ph.D.

Examples of Research

Marni Hall, Ph.D.

Accessing Data

Maria Owings, Ph.D.

New Directions

Bob Pokras



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NHDS Survey Years

  • Conducted annually 1965-present:

    • Latest data available: 2002

    • 2003 will be available this Winter


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NHDS Survey Design

  • National probability sample:

    • Short stay non-Federal hospitals

  • Three stage design:

    1. Geographic units

    2. Hospital

    3. Discharge


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More Information on NHDS Design and Operations

  • NCHS Publications: Series 1, No. 39

    “Design and Operation of the National Hospital Discharge Survey: 1988 Redesign”

http://www.cdc.gov/nchs/data/series/sr_01/sr01_039.pdf


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NHDS Sample Size

  • Hospitals:

    • About 500 hospitals sampled per year

  • Discharges:

    • Over 300,000 sampled per year


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NHDS Data Collection

  • Manual hospitals - 60%

  • Automated hospitals - 40%


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NHDS Manual Data Collection

  • NCHS – Statistical Design

  • Census Bureau – Field Work

  • Contractor – Coding and Data Entry


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NHDS Automated Data Collection

  • Electronic files obtained from:

    • States

    • Commercial firms

    • Individual hospitals


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NHDS Data Processing

  • NCHS:

    • Editing

    • Estimation


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NHDS Estimation

  • Weight:

    • Inverse of the probability of selection

    • Adjustments for non-response

    • Population weighting ratio adjustment



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Variables onNHDS Public Use Data Files


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Patient Data

  • Age

  • Sex

  • Race

  • Expected source of payment

  • Discharge status

  • Marital status


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Hospital Characteristics

  • Geographic region

  • Bed size

  • Ownership


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Medical Data

  • Diagnoses and procedures

  • International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM)


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Additional Variables

  • Days of care

  • Month of discharge

  • DRG

  • Weight


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New Variables for NHDS

Available beginning in the 2001 NHDS:

- Source of Admission

- Type of Admission


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National Survey of Ambulatory Surgery (NSAS)

  • Survey Years: Annually 1994-1996

  • Collected data on ambulatory (outpatient)

    surgery in the U.S.


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NSAS Design

  • National probability sample

    • Short stay non-Federal hospitals (418)

    • Freestanding ambulatory surgery centers (333)

  • Sample size:

    • 120,000 sampled visits per year


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More Information on NSAS Design and Operations

  • Survey Design and Operations:

    NCHS Publications: Series 1, No. 37

    “Plan and Operation of the National Survey of Ambulatory Surgery”

    http://www.cdc.gov/nchs/data/series/sr_01/sr01_037.pdf


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Additional Variables Collected for NSAS

  • Hospital vs. freestanding center

  • Type of anesthesia

  • Anesthesia provider


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Analytic Issues

Lola Jean Kozak, Ph.D.


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Topics

  • Utilization measures

  • Medical coding system

  • Statistical issues


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NHDS provides data on

hospitalizations

not people


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Measures Include:

  • Discharges

  • Days of care

  • Average length of stay

  • Diagnoses

  • Surgeries/procedures


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Discharges

  • Include deaths

  • Include transfers to other hospitals or long-term care facilities

  • Do not usually include newborn infants


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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.


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Diagnoses

  • Disease, injury or other reason for hospitalization

  • Coded according to US adaptations of the

    International Classification of Diseases (ICD-9-CM)


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Diagnoses

  • Principal diagnosis: chiefly responsible for hospitalization

  • First-listed diagnosis: principal if specified, otherwise one listed first


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Diagnoses

  • All-listed: total number of times diagnoses appears on record

  • Any-listed: discharges with diagnosis in any position on record


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Hospital discharges with fractures, 2002

1,609,000

1,387,000

995,000

Principal or first listed

Any listed

All listed


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Surgery/Procedures

  • Surgical (appendectomy)

  • Diagnostic (spinal tap)

  • Therapeutic (chemotherapy) procedures

  • Coded according to US adaptations of the International Classification of Diseases


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NHDS provides data on

inpatient procedures

not total procedures


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Versions of the International Classification of Diseases

  • 8th revision used 1970-78

  • 9th revision used 1979-2004

  • 10th revision for use in future


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8th Revision

  • Some codes different than in 9th Revision

  • Did not use E-codes

  • Made modifications in coding to accommodate available data


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9th Revision

  • Addenda added annually since 1986

  • Codes added, deleted, expanded, and revised

  • Lists of changes available in annual summary reports, file documentation


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Weights

  • Must use weighted data to obtain unbiased national estimates.

  • Each record has a weight

  • Sum the weights of the records


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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.


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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



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65 and over Survey

45-64

All ages

15-44

Under 15

Average length of hospital stay by age, 1970-2001


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65 and over Survey

45-64

15-44

< 15

1970

1980

1990

2002

Percent distribution of hospital inpatients by age


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

Jean Kozak

Long-Term Care Interface – June 2002


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2.8 Million 1990’s

1.6 Million

Transfers to long-term care,1990-1999

Number in Millions


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12.8 days 1990’s

8.3 days

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


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Examples of 1990’shealth services research:

  • Long-stay patients in short-stay hospitalsAcademyHealth Annual Meeting Presentation - Marni Hall and Maria Owings - June, 2003

  • Admit source and type

    NAHDO Annual Meeting Presentation - Maria Owings and Marni Hall - December 2003

  • Differences in length of stay in Veterans Health Administration and NHDS hospitalsMedical Care - GE Rosenthal et al. - August 2003


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Common NHDS Research Topics: 1990’s

  • Deliveries

    • Type of birth, e.g. cesarean section

    • Obstetrical procedures

    • Length of stay


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U.S. Trends in Obstetric Procedures, 1990-2000 1990’s

Jean Kozak and Julie Weeks

Birth – September 2002


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26.8 1990’s

16.5

Rate of cesarean sections,1980-2002


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15.8 1990’s

6.6

Rate of vaginal birth after cesarean section, 1990-2002


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Common NHDS Research Topics (con’d): 1990’s

  • Newborns

    • Premature

    • Sick/well – common diagnoses

    • Length of stay in hospital


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4.3 days 1990’s

3.2 days

Average length of stay for newborns,1980-2002


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Recent diagnoses studied 1990’s

Heart failureAtrial fibrillationArthritisPneumoniaMental disorders in childrenSepsis


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201.4 1990’s

133.4

Rate of hospitalization for congestive heart failure for those 65 and over, 1980-2002


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Recent procedures studied: 1990’s

Hip replacementsKnee replacementsCoronary artery revascularization proceduresCervical diskectomy


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67.6 1990’s

38.2

Rate of knee replacement for inpatients 65 years and older, 1991-2002


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Example of trend analyses related to public health 1990’s

Chartbook on Trends in Injury Hospitalizations

United States, 1979-2001

Melissa Heinen, Marni Hall, Manon Boudreault,

Lois Fingerhut

NCHS Publication

Available in the Fall of 2004


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85 and over 1990’s

75-84

65-74

Data are plotted on the log scale.

Rate of hospitalization for hip fracture for females 65 and over, 1980-2001


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Other Public Health/ 1990’sMedical Care Research

DiabetesAsthmaObesityHypertensionChronic Obstructive Pulmonary Disease (COPD)


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Other publications using NHDS trend data: 1990’s

Health Care in America. Trends in Utilization,

2004

http://www.cdc.gov/nchs/pressroom/04facts/healthcare.htm

Health United States, 2003

http://www.cdc.gov/nchs/hus.htm

Healthy People 2010

http://www.cdc.gov/nchs/hphome.htm


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For more information see: 1990’s

Internet Resources: Hospital Discharge and Ambulatory Surgery Data (handout)


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Accessing Data from the 1990’sNational Hospital Discharge Survey

Maria Owings, Ph.D.


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What type of data are available? 1990’s

  • Publications, including annual reports

  • Data tabulations on selected topics

  • Public-use data files (micro-data)


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How Can I Obtain Data from the 1990’sNational Hospital Discharge Survey?

  • Go to the Hospital Discharge and Ambulatory Surgery homepage on the Web: www.cdc.gov/nchs/about/major/hdasd/nhds.htm

  • Telephone the Hospital Care Statistics Branch: 301-458-4321

  • Contact NCHS Information Dissemination Staff 1-866-441-NCHS (toll free)

  • Send an email to: [email protected]


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Annual Publications from 1990’sHospital Care Statistics Branch

  • ADVANCE DATA reports:

    • Provide early release of NHDS data

    • Are very general and usually short

    • 2002: http://www.cdc.gov/nchs/data/ad/ad342.pdf

  • VITAL AND HEALTH STATISTICS Series 13 reports, e.g. Annual Summary and Detailed Reports

    • Provide more comprehensive statistics on utilization

    • Contain detailed tables of diagnoses and procedures

    • 2001: http://www.cdc.gov/nchs/data/series/sr_13/

      sr13_156.pdf


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Navigating the NCHS Website 1990’s

  • Several avenues are available to find data and reports on NHDS and NSAS

  • Know what you are looking for, e.g.

    • Microdata files & documentation

    • Published reports & tabulations

  • Follow links – many lead to the same place


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What to Know to Access 1990’sData and Publications on the Web

  • 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

  • Data files are in ASCII format and must be downloaded via FTP server

  • After downloading, files must be “unzipped” using WINZIP or other data extraction software, available for free


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Links from the NCHS Homepage: 1990’swww.cdc.gov/nchs

  • Surveys & Data Collection Systems

    • National Health Care Survey, e.g.

      NHDS & NSAS

  • Publications & Information Products

    • Published reports & Data Warehouse

  • Micro-data Access

    • Public Use Data Files & Documentation


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NHDS & NSAS Homepage 1990’s

  • http://www.cdc.gov/nchs/about/major/hdasd/

    nhds.htm

    provides links to all aspects of survey design, public use data, and dissemination products, including

    • Survey Description & Methodology

    • New Releases & Fact Sheets

    • NCHS Health E-Stats

    • Data Highlights & Selected Tables

    • Publications: reports and journal articles

    • Public Use Data Files (microdata)


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Links to NHDS and NSAS 1990’sPublications on the Web

  • http://www.cdc.gov/nchs/about/major/hdasd/

    listpubs.htm

    Lists annual publications and special topic reports by name and number (back to 1990 only)

  • http://www.cdc.gov/nchs/products.htm

    Lists electronic products available for entire Center, including NHDS & NSAS products

  • AD & Series 13 reports cataloged by number,

    not name (some back to 1960’s)

  • Links to Data Warehouse


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Data Warehouse 1990’s

  • http://www.cdc.gov/nchs/datawh.htm

    Provides links by topic area for all NCHS products

    (not just NHDS & NSAS), including

    • Public Use Files & Documentation

    • Published Reports, by type

      e.g. Advance Data, Vital and Health Statistics Series 13 , etc (need to know report number)

    • ICD-9-CM coding index

  • http://www.cdc.gov/nchs/datawh/ftpserv/ftpdata/

    ftpdata.htm[ FTP server ]


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    Public-Use Files 1990’sAvailable on the Web

    • Data and documentation available for free from the NCHS website

      • NHDS: 1996 through 2002

      • NSAS: 1994, 1995, 1996

    • Files are “raw” ASCII data that require the use of standard statistical software packages, such as SAS, SPSS, Stata, etc.


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    What to Know to Access 1990’sPublic-Use Files on the Web

    • Downloadable public-use data files are “zipped” for a speedier download

    • “Unzip” these files with

      • WinZip (www.winzip.com)

      • PKunzip (www.pkware.com)

    • Data file documentation is available in PDF format


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    Public-Use Files 1990’sAvailable on CD-ROM

    • Single year files available for some years

      -- From NCHS, years 1990, 1994 to 1998

      -- From NTIS, years 1970 to 1998

    • Two separate multi-year files containing

      • 1979-2002 data years (ICD-9-CM coding)

      • 1970-1978 data years (ICD-8 coding)

        IMPORTANT: DRGs are available on single year files only. Multi-year files do NOT have DRGs.


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    How to Get PU Files on CD-ROM 1990’s

    • FREE from NCHS by contacting

      • NCHS Information Dissemination Staff :

        301-458-INFO or 1-866-441-NCHS

      • Hospital Care Statistics Branch: 301-458-4321

    • Purchased from National Technical Information Service (NTIS) *

      • phone 1-800-553-6847 or (703) 605-6000

      • online at www.ntis.gov

        * Annual files for single years prior to 1994 can only be obtained from NTIS (not available from NCHS)


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    ICD-9-CM 1990’s

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


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    Restricted Data in NHDS 1990’s

    • 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)

    • http://www.cdc.gov/nchs/r&d/rdc.htm


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    Through the RDC 1990’sResearchers Can Use:

    • Confidential files for NHDS and NSAS variance estimation

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


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    Confidential Variables Available 1990’sOnly 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

      **************************************

      NOTE: Identifiers such as patient name, address, and SSN are not collected in the NHDS


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    NHDS can be linked with other files 1990’s

    • 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)


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    Beyond 20/20 Browser 1990’s

    • 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


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    NHDS or NSAS Questions? 1990’s

    Phone: 301-458-4321

    Fax: 301-458-4032

    Email: [email protected]


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    New Directions 1990’sNational Hospital Discharge Survey

    Bob Pokras


    New directions l.jpg
    New Directions 1990’s

    • Internet Data

      • Beyond 20/20

      • Improved internet links

    • Linked files


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    New Directions 1990’s

    • Clinical data

    • Evaluation of drugs in the NHDS


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    NSAS and NHDS 1990’s

    • NSAS status

    • NHDS status


    Nhds and nsas l.jpg

    NHDS and NSAS 1990’s

    Carol DeFrances

    Jean Kozak

    Marni Hall

    Maria Owings

    Bob Pokras


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