National Hospital Ambulatory Medical Care Survey, 2005 (ICPSR 28261)

Published: Jun 8, 2010

Principal Investigator(s):
United States Department of Health and Human Services: National Center for Health Statistics


Version V1

The National Hospital Ambulatory Medical Care Survey (NHAMCS) provides data from samples of patient records selected from emergency departments (EDs) and outpatient departments (OPDs) of a national sample of hospitals. The resulting national estimates describe the use of hospital ambulatory medical care services in the United States. For the 2005 survey, data were collected from 205 OPDs and 417 EDs. Among the variables included are age, race, and sex of the patient, reason for the visit, physician's diagnoses, cause of injury, surgical procedures (OPDs only), medication therapy, and expected source of payment. For 2005, additional updates and revisions have been made to both the emergency department and outpatient department data, including modifications to preexisting variables and the inclusion of new variables pertaining but not limited to patient pregnancy, height, and weight.

United States Department of Health and Human Services: National Center for Health Statistics. National Hospital Ambulatory Medical Care Survey, 2005. Ann Arbor, MI: Inter-university Consortium for Political and Social Research [distributor], 2010-06-08.

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In preparing the data files for this collection, the National Center for Health Statistics (NCHS) has removed direct identifiers and characteristics that might lead to identification of data subjects. As an additional precaution NCHS requires, under Section 308(d) of the Public Health Service Act (42 U.S.C. 242m), that data collected by NCHS not be used for any purpose other than statistical analysis and reporting. NCHS further requires that analysts not use the data to learn the identity of any persons or establishments and that the director of NCHS be notified if any identities are inadvertently discovered. ICPSR member institutions and other users ordering data from ICPSR are expected to adhere to these restrictions.


2004-12-27 -- 2005-12-25

A numeric recode version of the diagnosis variables (DIAG1R, DIAG2R, DIAG3R) has been included in the data. Value labels have been added to the SAS and SPSS setup files. Users may verify the labeling of the numeric recode variables by referring to the character (string) format variables DIAG1, DIAG2, and DIAG3. Please consult the User Guide for detailed information regarding numeric recodes for cause of injury, diagnosis, and procedure codes.

Users should be aware that Stata will not allow value labels for character (string) format variables. The 2005 NHAMCS data contain a number of character variables (e.g., DIAG1, DIAG2, and DIAG3 -- physician's listed diagnosis codes).

Per agreement with the National Center for Health Statistics (NCHS), ICPSR distributes the data files and text of the technical documentation for this collection as prepared by NCHS.

Detailed information regarding the use of weight variables and variance estimation is located in the User Guide.

The National Hospital Ambulatory Medical Care Survey (NHAMCS) used a four-stage probability design with samples of primary sampling units (PSUs), hospitals within PSUs, clinics within hospitals, and patient visits within clinics.

Visits to the emergency and outpatient departments of noninstitutional general and short-stay hospitals within the 50 states and the District of Columbia, which had an average length of stay of less than 30 days, or to hospitals whose specialty was general (medical or surgical) or children's general. Excluded were federal hospitals, hospital units within institutions, and hospitals with less than six beds staffed for patient use.

Patient visit records from hospital emergency departments and outpatient departments.

administrative records data



2010-06-08 ICPSR data undergo a confidentiality review and are altered when necessary to limit the risk of disclosure. ICPSR also routinely creates ready-to-go data files along with setups in the major statistical software formats as well as standard codebooks to accompany the data. In addition to these procedures, ICPSR performed the following processing steps for this data collection:

  • Created variable labels and/or value labels.

Users should use the variable PATWT when performing analyses.


  • The public-use data files in this collection are available for access by the general public. Access does not require affiliation with an ICPSR member institution.

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This study is maintained and distributed by the National Archive of Computerized Data on Aging (NACDA), the aging program within ICPSR. NACDA is sponsored by the National Institute on Aging (NIA) at the National Institutes of Heath (NIH).