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

National Health Care Surveys Visits to –Doctors’ offices (NAMCS) –Emergency rooms (NHAMCS) –Outpatient departments (NHAMCS) Inpatients (NHDS) Ambulatory surgery (NSAS) ( ) Long term care –Nursing homes (NNHS) –Home health care (NHHCS) –Hospices (NHHCS)

Handout Internet Resources: Hospital Discharge and Ambulatory Surgery Data For an of this table of hotlinks, write to:

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

Survey Design and Operations NCHS Publications –NSAS – Series 1 No. 37 –NHDS – Series 1 No. 39

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 percent for hospitals 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

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, 9 th 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

Summary Source of the data –Design –Methods Variables

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 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 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 8 th revision used th revision used th revision for use in future

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

9 th 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 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, Number in Millions 1.6 Million 2.8 Million

Average hospital stay for long-term transfers, days 8.3 days

Hospital discharges transferred to long- term care institutions by length of stay, Hospital Stay Transfers in Thousands

Long-term transfers by first-listed diagnoses 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, 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 # of discharges 2,200,0003,700,000 million Rate per 1,000 population

Trend in rate of avoidable hospitalizations

Trend in rate of other hospitalizations

Trend in rate of avoidable hospitalizations Under 65 Over

Trend in rate of avoidable hospitalizations for those over 65 Whites Blacks

Trend in rate of avoidable hospitalizations for those under 65 Blacks Whites

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, and over

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, Rate per 10,000 population RuralUrban

Indicators of Severity of Illness UrbanRural Average # diagnoses % with serious comorbidities 36% 40% Average # serious comorbidities Significant Difference

UrbanRural Average age Average length of stay (days) Routine Discharge 70%65% 1 Significant difference Indicators of Severity of Illness

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

Active MD’sHospital Beds MD/Hospital Availability 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

$ 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 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 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: Send an to: Go to the NCHS website on the World Wide Web:

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 : NHDS Annual Summary : r13_151.pdf r13_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

Where to Find NHDS and NSAS Data and Pubs on the WWW Lists annual pubs (back to 1990 only) and special topic reports by name and number 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 provides links to all aspects of survey design, data, and dissemination, includinghttp:// –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 PKunzip at Data documentation are available either as text files or PDF files.

Public-Use Files Available on CD-ROM Two separate multi-year files containing – data years (ICD-9-CM coding) – 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: INFO Hospital Care Statistics Branch: Or ordered from National Technical Information Service (NTIS) by phone at or (703) online at 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 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)

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 ng/howto.htm#browser2http:// ng/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 d/nhdslistserv.htmhttp:// d/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 message (leaving the subject line blank), type: subscribe hdas-data your name Send this message to:

NHDS or NSAS Questions? Phone: Fax:

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