At a glance
- The National Hospital Ambulatory Medical Care Survey (NHAMCS) ended in 2022.
- NHAMCS collected data about medical services provided in hospital emergency and outpatient departments.
- NHAMCS data can answer questions about hospital-based medical care for patients who weren't admitted as inpatients (ambulatory medical care).
Overview
NHAMCS data collection stops
The National Hospital Ambulatory Medical Care Survey (NHAMCS) collected data about medical services for patients who were treated in hospital emergency and outpatient departments without being admitted to the hospital. Healthcare professionals call these services ambulatory medical care.
The National Center for Health Statistics (NCHS) launched NHAMCS in 1992. Data collection from hospital-based ambulatory surgery centers began in 2009. Ambulatory surgery centers provide same-day surgeries without admitting patients overnight. Between 2010 and 2012, NHAMCS also gathered data on visits to ambulatory surgery centers that weren't located at hospitals (freestanding 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.
Ending NHAMCS
NCHS conducted NHAMCS annually through 2022. The survey collected and released high quality, objective, reliable information about how hospital-based ambulatory medical care services were provided and used in the United States. To collect NHAMCS data, information was manually taken from medical records. Now, the widespread use of electronic health records allows this information to be shared electronically, including with public health authorities like NCHS, more easily.
In addition, other surveys now collect the data historically gathered by NHAMCS. For example, the National Hospital Care Survey collects data on emergency department use.
How the data were collected
In the last years of NHAMCS, approximately 500 hospitals provided data on a sample of patient visits from a 4-week reporting period. NHAMCS collected data about patients (age, race, sex, ethnicity) and their visits (reason, diagnosis, services, and treatments). Data about the facility were also collected as part of an introductory interview.
When additional types of facilities were part of NHAMCS, NCHS collected similar data for visits to hospital outpatient departments, hospital ambulatory surgery centers, and freestanding ambulatory surgery centers.
Data and documentation
NCHS has published reports, web tables, and other products featuring NHAMCS data. NCHS also provides an interactive dashboard featuring data about emergency department visits from 2016 through 2022. In producing these resources, NHAMCS staff prioritized protecting the privacy of participating hospitals and their patients.
Data file
NHAMCS public use data files are available to download in multiple formats. All potentially identifiable information has been removed to ensure the confidentiality of respondents and patients.
Restricted data files are available through the NCHS Research Data Center (RDC) for a fee. To access restricted NCHS data, researchers must submit requests in the Standard Application Process portal. The RDC provides instructions for preparing and submitting an application to access restricted data.
Find data documentation for these datasets in the Questionnaires, Data Sets, and Documentation section of this website.
How the data are used
Policy makers, researchers, medical schools, medical associations, public health professionals, and the media use NHAMCS data to understand health care in the United States. NHAMCS data can answer questions about what hospital-based medical care has been needed, how it has been provided, and how that changed over time.
NHAMCS data provide information about—
- Patients who use hospital emergency departments and outpatient departments
- Medical conditions most often seen in these settings
- Diagnosis and treatment services—including prescribing medications—provided in these settings
Analysts can use NHAMCS data to estimate national physician and medical visit statistics.
Medical diagnoses
NHAMCS data cannot be used to estimate how many people have received a specific diagnosis because the data are not representative of the nation's population. NHAMCS collected data based on a sample of visits rather than a sample of people.