2003 National Hospital Ambulatory Medical Care Survey Public Use

2003 NHAMCS MICRO-DATA FILE DOCUMENTATION PAGE 1 ABSTRACT This material provides documentation for users of the micro-data files of the 2003 National Hospital Ambulatory Medical Care Survey (NHAMCS). The NHAMCS is a national probability sample survey of visits to hospital outpatient and emergency departments, conducted by the National Center for Health Statistics, Centers for Disease Control and Prevention. The survey is a component of the National Health Care Survey, which measures health care utilization across a variety of health care providers. There are two micro-data files produced from the NHAMCS, one for outpatient department records and one for emergency department records. Section I of this documentation, “Description of the National Hospital Ambulatory Medical Care Survey,” includes information on the scope of the survey, the sample, field activities, data collection procedures, medical coding procedures, and population estimates. Section II provides detailed descriptions of the contents of each file’s data record by location. Section III contains marginal data for selected items on each file. The appendixes contain sampling errors, instructions and definitions for completing the Patient Record forms, and lists of codes used in the survey. PAGE 2 2003 NHAMCS MICRO-DATA FILE DOCUMENTATION SUMMARY OF CHANGES FOR 2003 The 2003 NHAMCS Outpatient Department and Emergency Department public use micro-data files are, for the most part, identical to the 2002 NHAMCS public use micro-data files. Changes are summarized below: Emergency Department Public Use File 1. New/Modified Items a. Waiting time to see physician [WAITTIME] - This is calculated from the patient’s time of arrival to the ED and the time seen by physician. It was last available on the 2000 public use file, when time seen by physician was last collected. b. Mode of Arrival [ARRIVE] - This was last collected in 2000. c. Oriented x 3 [ORIENTED] - This is a new item on the Patient Record form for 2003. It refers to the patient’s orientation to time, place, and person. d. Presenting level of pain [PAIN] - This was last collected in 2000. e. Is this visit work related? [VWORKREL] - This is a new item on the 2003 Patient Record form. Previously, work-relatedness was only asked about injuries f. Diagnostic/Screening Services – Electrolytes testing (ELECTROL] is a new category for 2003. g. Diagnostic/Screening Services – Other blood test [OTHERBLD] replaced Other blood chemistry [OTHBLDCH] on the Patient Record form in 2003. h. Diagnostic/Screening Services – Other test/service [OTHRTEST] replaced Other lab test [OTHERLAB] on the Patient Record form in 2003. i. Medications & Injections – increased drug entry fields from six to eight j. Patient ethnicity imputed? [ETHNICFL] - In 2003, missing data for patient ethnicity have been imputed. Ethnicity has not been imputed since 1996. A flag was added to identify the imputed records. 2. Deleted Items a. Is this injury or poisoning work related? [WORKREL] – Replaced by the broader question, Is this visit work related? See above. b. Is this visit related to an adverse drug event? [ADVDRUG, ADVDRUG1, ADVDRUG2 and drug characteristics for each adverse drug] – Not collected in 2003. c. Other blood chemistry [OTHBLDCH] – see above. d. Other lab test [OTHERLAB] – see above. Outpatient Department Public Use File 1. New/Modified Items a. Was patient’s temperature taken? [TEMPTAKE] – new for 2003. b. Temperature reading (Fahrenheit) [TEMPF] – new for 2003. c. Blood pressure reading (BPSYS, BPDIAS] – new for 2003. d. Diagnostic/screening services – Glucose test [GLUCOSE] is new for 2003. e. Diagnostic/screening services – Glycohemoglobin test [HGBA] is new for 2003. f. Diagnostic/Screening Services – Electrolytes test (ELECTROL] is new for 2003. g. Medications & Injections – increased drug entry fields from six to eight h. Patient ethnicity imputed? [ETHNICFL] - In 2003, missing data for patient ethnicity were imputed for the first time since 1996. A flag was added to identify the imputed records. i. “Has the patient been seen in this clinic before?” imputed? [SENBEFL] – In 2003, missing data for this item were imputed for the first time since 1996. A flag was added to identify the imputed records. 2003 NHAMCS MICRO-DATA FILE DOCUMENTATION PAGE 3 j. “If yes, how many past visits in the last 12 months?” imputed? [PASTFL] – In 2003, missing data for this item were imputed. A flag was added to identify the imputed records. Sample Design Variables As first stated in the 2002 NHAMCS public use file documentation, the multi-stage masked sample design variables used for variance estimation in SUDAAN are no longer included on the file. The variables, CSTRATM and CPSUM, which were first included in the 2002 release, take their place, and can be used to estimate variance with SUDAAN’s with-replacement (WR) option, as well as with Stata, SPSS, SAS, and other statistical software packages utilizing an ultimate cluster design for variance estimation. These variables and their use are described more fully in the “Relative Standard Errors” section of the public use file documentation. Drug Characteristics The Ambulatory Care Drug Database underwent substantial revisions in 2002, as described in the 2002 NHAMCS Public Use Data File Documentation. For 2003, we continued to add new drugs and update the database as necessary. Because of these revisions to the file, and also because of the addition of a second and third therapeutic class for each drug beginning in 2002, trend analysis with survey data prior to 2002 becomes more problematic. We recommend that researchers download the Drug Characteristics file, which is updated annually, from the Ambulatory Health Care Data website. The characteristics from this file can be applied by matching on drug codes to previous years of data in order to get the most accurate results when doing analysis of drug trends by therapeutic class. We recommend that you use the SAS program (which can be adapted for use with other software) that we have developed and which is downloadable at our website. This program will apply the new characteristics from the most current version of the drug database to previous years of data. Our website can be accessed at: http://www.cdc.gov/nchs/nhamcs.htm Reason for Visit Classification The Reason for Visit Classification, developed by NCHS to code the patient’s expressed reason for the medical visit, is updated periodically to reflect reasons for which codes were not previously available and to modify some existing codes to improve the classification scheme. The version of the classification used in a particular survey year is included in that year’s public use documentation. Because of the changes that occur over time, researchers are advised, when doing multi-year analysis involving reason for visit, to check each year’s classification to make sure they are using the best and most complete set of codes for their analysis. PAGE 4 2003 NHAMCS MICRO-DATA FILE DOCUMENTATION THIS PAGE HAS BEEN LEFT BLANK INTENTIONALLY. 2003 NHAMCS MICRO-DATA FILE DOCUMENTATION PAGE 5 Table of Contents Page Abstract ........................................................................................................................................................1 Summary of Changes for 2003 ....................................................................................................................2 I. Description of the National Hospital Ambulatory Medical Care Survey...............................................7 A. Introduction....................................................................................................................................8 B. Sample design.............................................................................................................................11 C. Data collection procedures ..........................................................................................................12 D. Field quality control......................................................................................................................12 E. Confidentiality ..............................................................................................................................12 F. Data processing...........................................................................................................................13 G. .Medical coding............................................................................................................................16 H. Estimation procedures.................................................................................................................19 I. Patient visit weight.......................................................................................................................20 J. Hospital code and patient code ...................................................................................................21 K. Clinic type code ...........................................................................................................................21 L. Population figures........................................................................................................................21 References .......................................................................................................................................26 II Record Formats A. Format of Emergency Department Micro-Data File .....................................................................27

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