Ambulatory Health Care Data

Notices for NAMCS and NHAMCS Public Use Data File Users

NAMCS Present and Future (as of 11/2022)

NAMCS has traditionally been a survey of office-based physicians and their visits. From 2006 to 2011, it also included a sample of visits to community health centers. In 2012, NAMCS initiated a separate and independent survey component of visits to health centers (currently referred to as the Health Center Component or HCC), and those data continue to be collected and released separately from the “traditional” NAMCS.

During the 2020 and 2021 NAMCS office-based physician data collection periods, only physician-level data were collected using the Physician Induction Interview. These files are available in the NCHS Research Data Center. The NAMCS office-based physician survey was not fielded in 2022. This survey will be fielded again in 2023 as the NAMCS Provider Component.  The survey has been redesigned and will be piloted as a mixed-mode (web and mail) survey that includes both physicians and physician assistants/associates (PAs) who provide ambulatory care. While provider-level data will be collected, there will be no visit data collected as part of the 2023 NAMCS Provider Component. It is expected that a public use file with 2023 NAMCS provider-level data will be released.  Visit data are planned to be included as part of the NAMCS office-based physician survey in the future, leveraging electronic health records and other electronic health data sources. In the meantime, NAMCS HCC continues to survey visits to health centers on an annual basis.

2018 NAMCS Public Use File Addendum

An addendum to the 2018 NAMCS public use data file documentation is now available, along with a SAS data set containing a refined version of the patient visit weight and the physician weight.  The addendum includes a program to merge the new variables to the existing 2018 NAMCS public use data file.  The refined weighting variables reflect changes made to the weighting methodology used with the 2019 NAMCS.  They are being provided should researchers wish to use the same methodology for both survey years. See the addendum for more information.

2020 NAMCS Community Health Center (CHC) Public Use Data File update

Because of limitations posed by the COVID-19 pandemic, the 2020 National Ambulatory Medical Care Survey (NAMCS) Community Health Center (CHC) Visit File will only be available in the NCHS Research Data Center (RDC). Please see the RDC file data dictionary [PDF – 684 KB], visit the RDC website, or contact the Ambulatory and Hospital Care Statistics Branch at ambcare@cdc.gov or 301-458-4600 for more information.

2020 NAMCS Public Use Data File Update

Due to the pandemic, visit data for office-based physicians were not able to be collected for most of 2020. Therefore, a visit-level public use file will not be available. Two physician-level files based on data from the 2020 National Ambulatory Medical Care Survey Physician Induction Interview are available for use in the NCHS Research Data Center (RDC). One of these is a small data file which includes physician responses for Periods 3 and 4 of the 2020 NAMCS data collection. Period 3 marked the first time COVID-19 questions were able to be fielded. Using this file allows researchers to replicate data found in the NAMCS COVID-19 Dashboard. The file includes special weights only for use with combined data from Periods 3 and 4 [PDF – 129 KB]. The second file is the complete physician level file which contains all of the standard data elements including weights to produce annual physician-level estimates. Please see the RDC file data dictionary [PDF – 458 KB], visit the RDC website, or contact the Ambulatory and Hospital Care Statistics Branch at ambcare@cdc.gov or 301-458-4600 for more information.

2017 NAMCS Public Use Data File Update

In 2016 and 2017, two modes of data collection were used for NAMCS. One was the traditional in-person, manual medical record abstraction by U.S. Census Bureau staff; the other was submission of electronic health records (EHR) directly by the sampled physician to NCHS. As a result, additional data processing was required; integration and harmonization of the data from these two modes of collection is ongoing.

NCHS was able to release national estimates for 2016 NAMCS for those physicians from whom data were collected through the traditional abstraction method. However, unlike the 2016 survey, the sampling design used for 2017 NAMCS requires that both abstracted and EHR data be integrated and harmonized so that national visit estimates can be produced. As noted earlier, this integration and harmonization is still ongoing.  Although 2017 NAMCS data were expected to be released in early 2021, the release of these data has been delayed, as preference has been given to data that address the ongoing COVID-19 pandemic.

A release date has not yet been scheduled for the 2017 NAMCS visit data, but the 2017 NAMCS Physician Induction Interview data were released as a physician-level file to NCHS and Federal Research Data Centers in November 2021.

NHAMCS Outpatient Department Data from 2012-2017

Due to quality assurance issues, NHAMCS Outpatient Department (OPD) data from 2012-2017 are currently on hold. We are exploring whether these data can be released. Due to budget constraints, OPD data were not collected from 2018-2020.

Masked Design Variables

Currently, NAMCS public-use files for 1993-2018 and NHAMCS public-use files for 1992-2020 contain sample design variables in masked form. The initial release of the 2000-2020 public-use files includes masked sample design variables. We re-released the 1993-99 NAMCS and 1992-99 NHAMCS files to include these variables. For re-released files, file names and layouts are essentially the same, but the design variables were appended to each file according to a generic file layout that is available for downloading.

For 1993-99 NAMCS and 1992-99 NHAMCS, be sure to download not only the original file documentation for each year, but also the supplemental files that explain the new sample design variables that have been added to each file. The supplemental files also include descriptions of any revisions that may have been made to the original data files.

Data users should note that, beginning with the 2002 public use files, two new masked design variables were added to the file, for use with statistical software that assumes a single stage of sampling. For the 2003 public use files and beyond, the decision was made to include only these two masked design variables for variance estimation. Therefore, 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. A technical paper, Using Ultimate Cluster Models with NAMCS and NHAMCS Public Use Files [PDF – 34 KB] gives instructions.

Possible Problems Downloading Data Files and Documentation

Some data users have experienced a problem when trying to open self-extracting compressed data files and documentation in .EXE format in survey years prior to 2003. They receive a message that the version of the file is not compatible with the version of Windows they are running. This is because the files were created when NCHS used a 32-bit version of Windows, but newer versions use a 64-bit version. One work-around for this problem involves the use of WinZip software. Save the file in your local directory as usual, but instead of double-clicking on the file name to access the data, right-click the file name, select WinZip and choose one of the options for file extraction. This will cause an uncompressed version of file to appear in the directory window. For the longer term, NCHS is working on producing a new version of the problem files. Please contact the Ambulatory and Hospital Care Statistics Branch if you have questions. (9/2014)

Supplemental Documentation Files for 1993-99 NAMCS and 1992-99 NHAMCS

For 1993-99 NAMCS and 1992-99 NHAMCS, be sure to download not only the original file documentation for each year, but also the supplemental files that explain the new sample design variables that have been added to each file. The supplemental files also include descriptions of any revisions that may have been made to the original data files.

Public Use Data File and Documentation Updates

Occasionally, revisions are made to either the Public Use Data Files or Public Use Data File Documentation.  Check these pages for more information:

Other Sources for NAMCS and NHAMCS Data

NAMCS and NHAMCS data can also be downloaded from the Inter-University Consortium for Political and Social Research (ICPSR).