Total number of days discharged patients spend in th

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National Hospital Discharge Survey(NHDS)

• National Survey of Ambulatory Surgery
• (NSAS)

Centers for Disease Control and Prevention
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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

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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)

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Handout

• Internet Resources Hospital Discharge and
  Ambulatory Surgery Data
• For an email of this table of hotlinks, write to
  NHDS_at_cdc.gov

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Survey Years

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

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Survey Design and Operations

• NCHS Publications
• NSAS Series 1 No. 37
• NHDS Series 1 No. 39

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Survey Design

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

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Survey Design

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

14
Facility Sample Size

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

15
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

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Data Collection

• NHDS
• Manual 60
• Automated 40
• NSAS
• All manual

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Manual Data Collection

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

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Automated Data Collection

• Purchase files
• States
• Commercial firms
• Individual hospitals

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Data Collection

• NCHS
• Editing
• Estimation

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Estimation

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

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Variables on 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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Facility Characteristics

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

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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

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

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New Variables for NHDS

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

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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

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Type of Admission

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

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Summary

• Source of the data
• Design
• Methods
• Variables

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

• Lola Jean Kozak, Ph.D.

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Topics

• Utilization measures
• Populations
• 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

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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

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Length of stay for women with deliveries 1995
and 2000
Discharges in thousands
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Diagnoses

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

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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, 2000
1,542,000
1,226,000
982,000
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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Procedures mainly performed in inpatient
settings, 1996
Appendectomy
Coronary artery bypass graft
Hysterectomy
Cesarean section
Number in thousands
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Procedures mainly performed in ambulatory
settings, 1996
Arthroscopy Of knee
D C
Endoscopy of large intestine
Insertion of lens
Number in thousands
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Population for Rates

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

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Versions of the International Classification of
Diseases

• 8th revision used 1970-78
• 9th revision used 1979-2002
• 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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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

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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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Examples of Research Using the National Hospital
Discharge Survey

• Marni Hall, Ph.D.

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Hospital Transfers to Long Term Care Facilities
in the 1990s

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

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Transfers to long-term care,1990-1999
Number in Millions
2.8 Million
1.6 Million
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Average hospital stay for long-term transfers,
1990-1999
12.8 days
8.3 days
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Hospital discharges transferred to long-term care
institutions by length of stay, 1990-1999
Hospital Stay
Transfers in Thousands
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Long-term transfers by first-listed diagnoses
Circulatory
Respiratory
Injury poisoning
Digestive
Musculoskeletal
Endocrine, metabolic
Genitourinary
Neoplasms
Infectious parasitic
Mental disorders
100
300
600
600
300
100
0
1990
1999
Number in thousands
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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

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Trends in Avoidable Hospitalization United
States, 1980-1998

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

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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

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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

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Avoidable hospitalizations

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

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Trend in rate of avoidable hospitalizations
133.8
99.2
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Trend in rate of other hospitalizations
157.8
103.1
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Trend in rate of avoidable hospitalizations
Over 65
573.5
364.6
Under 65
65
71.1
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Trend in rate of avoidable hospitalizations for
those over 65
564
Blacks
352.8
450
Whites
325.2
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Trend in rate of avoidable hospitalizations for
those under 65
Blacks
113.5
92.5
53.8
Whites
49.1
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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

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Pneumonia hospital discharge rate for the elderly
221.2
65 and over
Rate per 10,000
125.3
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Disparities in the Rate of Hospitalization for
Pneumonia Patients in Rural and Urban Areas

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

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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)

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Disparity in Urban/Rural Pneumonia
Hospitalizations, 2000
78.0
37.5
Rate per 10,000 population
Rural
Urban
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Indicators of Severity of Illness

• Urban Rural
• Average diagnoses 5.1 4.9
• with serious
• comorbidities 36 40
• Average seriouscomorbidities 1.2 1.31
• 1Significant Difference

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Indicators of Severity of Illness

• Urban Rural
• Average age 59 641
• Average length of 6.2 5.31stay
  (days)
• Routine Discharge 70 65
• 1Significant difference

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Education, Unemployment and Poverty
w/some college
Unemployment rate
in poverty


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MD/Hospital Availability
Rate per 1,000 elderly

Active MDs
Hospital Beds

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Rate per 1,000 elderly
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What policies could reduce avoidable
hospitalizations?

• Promotion of rural managed care
• Programs which attract/keep rural MDs
• More affordable, accessible outpatient health
  care
• More health education / outreach programs - e.g.
  smoking cessation, influenza / pneumonia shots

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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

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

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

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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

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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

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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

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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

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Total hospital expenditures attributed to
hypertension
4.2 billion - diagnosis of hypertension
17.1 billion - cardiovascular complications
24.2 billion - other diagnoses __________________
_________________ 45.5 billion total hospital
expenditures attributed to hypertension
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Expenditures for hypertension, 1998
Home health care 4
Nursing home 12
Hospital care 42
Prescription Drugs 17
Physician Services 26
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Total expenditures attributed to hypertension

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

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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

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For more information see our Internet Resources
handout
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Accessing Data from NHDS and NSAS

• Maria Owings, Ph.D.

Centers for Disease Control and Prevention
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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

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Quick and Easy Access to NHDS and NSAS Data

• Telephone the Hospital Care Statistics Branch
  301-458-4321
• Send an email to NHDS_at_cdc.gov
• Go to the NCHS website on the World Wide Web
  www.cdc.gov/nchs

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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

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Recent Annual Publications

• 2000 NHDS Advance Data http//www.cdc.gov/nchs/d
  ata/ad/ad329.pdf
• 1999 NHDS Annual Summary 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

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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

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

• http//www.cdc.gov/nchs/about/major/hdasd/listpub
  s.htm
• Lists annual pubs (back to 1990 only) and special
  topic reports by name and number
• 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

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NHDS NSAS Homepage

• 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

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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.

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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.winzip.com/
• PKunzip at http//www.pkware.com/
• Data documentation are available either as text
  files or PDF files.

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Public-Use Files Available onCD-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.

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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 [phone]
• online at http//www.ntis.gov/
• Annual files for single years prior to 1994 can
  be ordered from NTIS, not directly from NCHS

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ICD-9-CM

• 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

• 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/rd/rdc.htm

108
Through the RDCResearchers Can Use

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

109
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

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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

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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

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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

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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)

114
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

115
Types of Variables in AHA

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

116
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.

117
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

118
Beyond 20/20 Browser

• http//www.cdc.gov/nchs/about/otheract/aging/howto
  .htmbrowser2
• 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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Listserv

•  http//www.cdc.gov/nchs/about/major/hdasd/nhdslis
  tserv.htm
• Provides current information about new data
  releases and publications
• Subscribers can post messages to other members
  and exchange information

120
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_at_cdc.gov

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NHDS or NSAS Questions?

• Phone [phone]
• Fax [phone]
• Email NHDS_at_cdc.gov

122
New Directions

• Beyond 20/20
• Public use variance file

123
New Directions

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