NHAMCS Questionnaires, Datasets, and Documentation

Overview

This section of the National Hospital Ambulatory Medical Care Survey (NHAMCS) website features questionnaires (survey instruments), data documentation, and other detailed technical information. These resources provide information about each NHAMCS data collection, their participants, and their protocols, as well as other analytic notes and references. They will help you understand, analyze, and use NHAMCS data.

The 2022 NHAMCS was the last data collection for this survey. This section of the website includes materials from the 2018–2022 NHAMCS. Survey instruments used to collect 2022 data can be found on this page.

Find survey instruments, data, and other resources from other recent NHAMCS years at—

• 2021 NHAMCS Questionnaires, Datasets, and Documentation
• 2020 NHAMCS Questionnaires, Datasets, and Documentation
• 2019 NHAMCS Questionnaires, Datasets, and Documentation
• 2018 NHAMCS Questionnaires, Datasets, and Documentation

Resources from earlier survey years are available through the CDC Archive. There you will find older questionnaires, datasets, and documentation for public use, and supporting materials for restricted data.

Data collection

The National Center for Health Statistics (NCHS) fielded NHAMCS annually from 1992 to 2022. NHAMCS collected data about how ambulatory care services were provided and used in hospital emergency and outpatient departments.

Data collection from hospital-based ambulatory surgery centers began in 2009. Between 2010 and 2012 NHAMCS gathered data on visits to freestanding ambulatory surgery centers. In 2018, NHAMCS stopped collecting data from outpatient departments. In its last five years (2018–2022), NHAMCS only collected data about ambulatory visits to emergency departments.

NCHS has not released outpatient data from 2012–2017 because of concerns about the quality of the data. We continue to explore options for sharing these data in the future.

Each year, approximately 500 nationally representative hospitals provided data on a sample of patient visits. Participating hospitals completed an introductory (induction) interview to determine how many ambulatory care visits they received each year. Sample data were then collected over a 4-week reporting period.

After data collection, information gathered in the induction interview also was used to weight data to reflect accurately the characteristics of all U.S. hospitals.

2022 NHAMCS

Emergency departments

Public use files

• Technical documentation
• ReadMe file
• SAS files
• Stata files

Drug ingredients

With the release of the 2022 NHAMCS public use data file, NCHS also has posted a SAS program to assist users who want to compare drug data from before and after 2006. In 2006, NCHS began using Lexicon Plus®, a proprietary database of Cerner Multum, Inc, to code drug characteristics in NHAMCS.

To make these comparisons possible, the SAS program does three things:

• Reads data in a pre-2006 year NHAMCS dataset
• Matches medication codes from that dataset with codes from the current ambulatory care drug database
• Replaces the old drug characteristics with the new Multum characteristics

Masked design variables

NHAMCS public use data files for 1992–2022 contain sample design variables in masked form. The 2000–2022 public use files included masked sample design when first released.

Beginning with the 2002 public use files, two new masked design variables were added to the file. These new masked design variables should be used with statistical software that assumes a single stage of sampling. Since 2003, NHAMCS has only included these two masked design variables for variance estimation. Data users who wish to combine years of data from 2003 and beyond with years prior to 2002 will need to create these two variables for each file prior to 2002.

Find instructions for creating these variables in Using Ultimate Cluster Models with NHAMCS Public Use Files.

Survey instruments

• Emergency department patient record questions (sample card)
• Hospital induction interview questions