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

1
National Hospital Discharge Survey (NHDS) and
National Survey of Ambulatory Surgery (NSAS)

• 2006 Data Users Conference
• July 10, 2006
• 330pm-500pm
• Session 15

2
Session Overview

• 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

3
Overview of the National Hospital Discharge
Survey(NHDS)

• Carol DeFrances, PhD

4
NHDS Survey Years

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

5
NHDS Survey Design

• Scope and coverage
• Short stay, non-Federal hospitals
• ALOS lt 30 days
• General and childrens general hospitals

6
NHDS Sampling Plan

• Three stage design
• Geographic units
• Hospital
• Discharge

7
NHDS Sample Size

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

8
NHDS Data Collection

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

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
Variables onNHDS Public Use Data Files
14
Patient Data

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

15
Hospital Characteristics

• Geographic region
• Bed size
• Ownership

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Medical Data

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

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Additional Variables

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

18
New Variables for NHDS

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

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New Variables for the NHDS

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

20
Analytic Issues

• Karen Lees, MPH

21
Topics

• Utilization measures
• Medical coding system
• Statistical issues

22

• NHDS provides data on
• hospitalizations
• not people

23
Measures Include

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

24
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

29
Hospital discharges with fractures, 2004
Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
30
Surgery / Procedures

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

31

• 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-present
• 10th revision for use in future

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ICD 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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ICD 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

38
Examples of Research

• Jean Kozak, Ph.D.

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Percent distribution of discharges and days of
care by age, 2004
Days of care
Discharges
85 and over
75-84
65-74
55-64
Age in years
45-54
35-44
25-34
15-24
5-14
0-4
0
10
10
20
20
Percent distribution
Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
40
Average length of hospital stay by age, 1980-2004

Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
41
Percent of hospital inpatients transferred to
long-term care facilities, by age, 1990-2004
Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
42
Hospitalization rates for major diagnostic
categories by sex, 2004
Males
Females
Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
43
Percent distribution of patients hospitalized for
heart disease, 2003
All other diagnoses 87
Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
44
Hospitalization rate for cancer,1990-2004
1990 63.0
2004 41.2
Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
45
Number of discharges with HIV diagnoses by age,
1995, 2000 and 2004
Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
46
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)
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Hospitalization rates for inpatients with
Clostridium difficile by age, 1996-2003
Source McDonald LC, et al. Emerg Infect Dis.
200612(3) 410-5.
48

Hospitalization rates for avoidable conditions by
race, patients under 65 years of age, 1990-2004
Black patients
White patients
Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
49
Average length of stay for selected diagnostic
categories, 2004
Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
50
Average length of stay for hip fractures,
1990-2004
12.8 days
1990
6.4 days
2004
Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
51
Length of hospitalization for childbirth,
1980-2004
Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
52
Rate of cardiac catheterizations by sex, age, and
geographic region, 2004

Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
53
Coronary artery bypass grafts (CABGs) and
percutaneous coronary interventions
(PCIs),1980-2004
Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
54
Percent distribution of white and black
discharges with coronary angioplasty according to
stent use, 2003
30.5
22.0
Black patients
White patients
Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
55
Hospitalization rates for obese patients with
gastric bypass, 1998-2003
Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
56
Rate of cesarean delivery, 1970-2004
2004 29.9
1970 5.5
Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
57
Rate of vaginal birth after cesarean (VBAC),
1990-2004
1990 20.4
2004 10.9
Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
58
Rate of forceps and vacuum extraction, 1990-2004
Vacuum
Forceps
Source CDC/NCHS, National Hospital Discharge
Survey (NHDS)
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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

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Accessing Data from the National Hospital
Discharge Survey

• Marni Hall, Ph.D.

61
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

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

• Youll 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

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

• 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

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(No Transcript)
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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

66
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

67
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

68
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)
• PKunzip (www.pkware.com)

69
Analyzing Public Use Data

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

70
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)
• DRGs are not included on the multi-year files.
• For NSAS a 1994-1996 data file is available.

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

• 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

72
Publications and Information Products

• http//www.cdc.gov/nchs/products.htm
• Lists electronic products
• Additional Information about obtaining reports,
  data, and other products

73
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

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Restricted Data in NHDS

• http//www.cdc.gov/nchs/rd/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)

75
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

76
Confidential Variables Available only on
Restricted Files

• 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

77
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

78
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_at_cdc.gov

79
Future Activities and Directions

• Robert Pokras, MA

80
Future Activities and Directions

• Redesigning the NHDS
• Refielding the NSAS

81
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

82
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

83
Highest Rated Options for Redesign

• 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

84
Clinical Depth Core Data Set(All Sampled Cases)

• Height
• Weight
• Administered drugs

85
Clinical DepthDiagnostic/ Procedure/
DemographicModule (Subsample of Cases)

• Lab values
• Pathology results

86
Resource Use/ Cost/ Efficiency

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

87
Improved Patient Demographics

• Race
• Ethnicity

88
Link to Health-Related Outcomes

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

89
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

90
Next Steps

• 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

91
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

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Breast lumpectomy procedures
?
Total
.
.
.
.
Ambulatory
Inpatient
Sources CDC/NCHS, National Survey of Ambulatory
Surgery (NSAS) and National Hospital Discharge
Survey (NHDS)
93
Any questions?