Include deaths. Include transfers to other hospitals o

1
National Hospital Discharge Survey(NHDS)
2
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

3
Overview of the National Hospital Discharge
Survey(NHDS)

• Carol DeFrances, Ph.D.

4
NHDS Survey Years

• Conducted annually 1965-present
• Latest data available 2002
• 2003 will be available this Winter

5
NHDS Survey Design

• National probability sample
• Short stay non-Federal hospitals
• Three stage design
• 1. Geographic units
• 2. Hospital
• 3. Discharge

6
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
7
NHDS Sample Size

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

8
NHDS Data Collection

• Manual hospitals - 60
• Automated hospitals - 40

9
NHDS Manual Data Collection

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

10
NHDS Automated Data Collection

• Electronic files obtained from
• States
• Commercial firms
• Individual hospitals

11
NHDS Data Processing

• NCHS
• Editing
• Estimation

12
NHDS Estimation

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

13
Health Insurance Portability and Accountability
Act (HIPAA)

14
Variables onNHDS Public Use Data Files

15
Patient Data

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

16
Hospital Characteristics

• Geographic region
• Bed size
• Ownership

17
Medical Data

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

18
Additional Variables

• Days of care
• Month of discharge
• DRG
• Weight

19
New Variables for NHDS

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

20
National Survey of Ambulatory Surgery (NSAS)

• Survey Years Annually 1994-1996
• Collected data on ambulatory (outpatient)
• surgery in the U.S.

21
NSAS Design

• National probability sample
• Short stay non-Federal hospitals (418)
• Freestanding ambulatory surgery centers
  (333)
• Sample size
• 120,000 sampled visits per year

22
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_03
  7.pdf

23
Additional Variables Collected for NSAS

• Hospital vs. freestanding center
• Type of anesthesia
• Anesthesia provider

24
Analytic Issues

• Lola Jean Kozak, Ph.D.

25
Topics

• Utilization measures
• Medical coding system
• Statistical issues

26
NHDS provides data on

• hospitalizations
• not people

27
Measures Include

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

28
Discharges

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

29
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.

30
Diagnoses

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

31
Diagnoses

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

32
Diagnoses

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

33
Hospital discharges with fractures, 2002
1,609,000
1,387,000
995,000
Principal or first listed
Any listed
All listed
34
Surgery/Procedures

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

35
NHDS provides data on

• inpatient procedures
• not total procedures

36
Versions of the International Classification of
Diseases

• 8th revision used 1970-78
• 9th revision used 1979-2004
• 10th revision for use in future

37
8th Revision

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

38
9th Revision

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

39
Weights

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

40
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.

41
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

42
Examples of Research Using the National Hospital
Discharge Survey

• Marni Hall, Ph.D.

43
Average length of hospital stay by age, 1970-2001
44
Percent distribution of hospital inpatients by age


45
Hospital Transfers to Long Term Care Facilities
in the 1990s

• Jean Kozak
• Long-Term Care Interface June 2002

46
Transfers to long-term care,1990-1999
Number in Millions
47
Average hospital stay for long-term transfers,
1990-1999
48
Examples of health services research

• Long-stay patients in short-stay hospitals
  AcademyHealth 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 hospitals Medical Care -
  GE Rosenthal et al. - August 2003

49
Common NHDS Research Topics

• Deliveries
• Type of birth, e.g. cesarean section
• Obstetrical procedures
• Length of stay

50
U.S. Trends in Obstetric Procedures, 1990-2000

• Jean Kozak and Julie Weeks
• Birth September 2002

51
Rate of cesarean sections,1980-2002
52
Rate of vaginal birth after cesarean section,
1990-2002
53
Common NHDS Research Topics (cond)

• Newborns
• Premature
• Sick/well common diagnoses
• Length of stay in hospital

54
Average length of stay for newborns,1980-2002
55
Recent diagnoses studied

• Heart failureAtrial fibrillationArthritisPneumo
  niaMental disorders in childrenSepsis

56
Rate of hospitalization for congestive heart
failure for those 65 and over, 1980-2002
57
Recent procedures studied

• Hip replacementsKnee replacementsCoronary
  artery revascularization proceduresCervical
  diskectomy

58
Rate of knee replacement for inpatients 65 years
and older, 1991-2002
59
Example of trend analyses related to public
health 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
60
Rate of hospitalization for hip fracture for
females 65 and over, 1980-2001
61
Other Public Health/Medical Care Research

• DiabetesAsthmaObesityHypertensionChronic
  Obstructive Pulmonary Disease (COPD)

62
Other publications using NHDS trend data Health
Care in America. Trends in Utilization,
2004 http//www.cdc.gov/nchs/pressroom/04facts/hea
lthcare.htm Health United States,
2003 http//www.cdc.gov/nchs/hus.htm Healthy
People 2010 http//www.cdc.gov/nchs/hphome.htm
63
For more information see

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

64
Accessing Data from the National Hospital
Discharge Survey

• Maria Owings, Ph.D.

65
What type of data are available?

• Publications, including annual reports
• Data tabulations on selected topics
• Public-use data files (micro-data)

66
How Can I Obtain Data from theNational Hospital
Discharge Survey?

• Go to the Hospital Discharge and Ambulatory
  Surgery homepage on the Web www.cdc.gov/nchs/abou
  t/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 NHDS_at_cdc.gov

67
Annual Publications fromHospital 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

68
Navigating the NCHS Website

• 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

69
What to Know to Access Data 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

70
Links from the NCHS Homepagewww.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

71
NHDS NSAS Homepage

• 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)

72
Links to NHDS and NSAS Publications 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 1960s)
• Links to Data Warehouse

73
Data Warehouse

• 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

74
Public-Use Files Available 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.

75
What to Know to Access Public-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

76
Public-Use Files Available 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.

77
How to Get PU Files on CD-ROM

• 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 [phone] or [phone]
• online at www.ntis.gov
• Annual files for single years prior to 1994
  can only be obtained from NTIS (not available
  from NCHS)

78
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.

79
Restricted Data in NHDS

• 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/rd/rdc.htm

80
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

81
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
• NOTE Identifiers such as patient name,
  address, and SSN are not collected in the NHDS

82
NHDS can be linked with other 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)

83
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

84
NHDS or NSAS Questions?

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

85
New Directions National Hospital Discharge Survey

• Bob Pokras

86
New Directions

• Internet Data
• Beyond 20/20
• Improved internet links
• Linked files

87
New Directions

• Clinical data
• Evaluation of drugs in the NHDS

88
NSAS and NHDS

• NSAS status
• NHDS status

89
NHDS and NSAS

• Carol DeFrances
• Jean Kozak
• Marni Hall
• Maria Owings
• Bob Pokras