Welcome NHAMCS Participants

The National Health Care Surveys (including NAMCS, NHAMCS, and NHCS) are working with the Centers for Medicare and Medicaid Services Electronic Health Record Incentive Programs: Promoting Interoperability (PI) (formerly known as Meaningful Use (MU)) and the Merit-based Incentive Payment System (MIPS). Click here to find out more.


Contact Information

If you have any questions or comments related to participation, please contact us at:

Ambulatory and Hospital Care Statistics Branch
National Center for Health Statistics
3311 Toledo Road
Hyattsville, Maryland 20782
Phone: 301-458-4600
Fax: 301-458-4032

Contact CDC-INFO


What is NHAMCS?

The National Hospital Ambulatory Medical Care Survey (NHAMCS) is the Nation’s foremost study of ambulatory medical care in hospital emergency and outpatient departments and has been conducted annually since 1992. Since 2018, the survey has been collecting data on only emergency department visits.

Each year, approximately 500 nationally representative hospitals provide data on a sample of patient visits. Sample data are collected over a 4-week reporting period. These collected data are weighted to produce national estimates which are widely used by health care researchers, policy analysts, congressional staff, the news media, and many others to improve our knowledge of medical practice patterns.

Reliable NHAMCS data and these national estimates depend on complete reports from all sampled hospitals.




Who is eligible to participate?

Hospitals eligible for participation in NHAMCS include those who are non-Federal general and short-stay hospitals, located in the 50 states or the District of Columbia, and have a 24-hour ED. Participation in NHAMCS is voluntary.


Why participate?

Your facility was randomly chosen to provide representative data not only for its own ESAs, but also for similar hospitals in the same geographic region. By participating in NHAMCS, you help provide a yearly national description of hospital-based ambulatory medical care services in the United States.


What are the benefits of participating?

Your hospital’s participation will result in more reliable statistics and will enable researchers to better measure the utilization and provision hospital-based ambulatory medical services.  The need for more complete data has been accentuated by the national opioid crisis, COVID-19 pandemic, the rapidly aging population, and use of innovative medical technologies. Failure to participate lessens the accuracy of the data used by researchers.


How does the process work?

Hospitals are chosen for participation through a random selection process. Letters informing hospital administrators about the purpose of the study are sent first. Next, the administrator is typically contacted over the phone by a U.S. Census Bureau field representative (FR) who confirms that the hospital is eligible for participation. Sometimes this initial contact happens in person. Once a hospital is confirmed eligible, the FR will conduct a brief interview with hospital staff to determine the visit volumes at each of the EDs in the hospital.

The U.S. Census Bureau FR will abstract only a sample of the patient visits that occurred during the hospital’s assigned reporting period. NCHS places high priority on protecting facility and patient confidentiality and adhering to the requirements of HIPAA. All information is collected in a way that protects respondents’ identities. As part of our data quality process, we conduct a data quality check on the responses obtained during the hospital interview.

If you would like more information on participation, please contact the Ambulatory and Hospital Care Statistics Branch (AHCSB) at 301-458-4600 or email or visit our Ambulatory Health Care Data home page.


Confidentiality and Privacy


Confidentiality of NHAMCS data

NCHS is legally bound to assure the confidentiality of all responses, including any information that might result in a health care provider or hospital being identified. The data files that are released for research do not include any provider, hospital or patient identifying information.

We take your privacy very seriously. All information that relates to or describes identifiable characteristics of individuals, a practice, or an establishment will be used only for statistical purposes. NCHS staff, contractors, and agents will not disclose or release responses in identifiable form without the consent of the individual or establishment in accordance with section 308(d) of the Public Health Service Act (42 U.S.C. 242m(d)) and the Confidential Information Protection and Statistical Efficiency Act of 2002 (CIPSEA, 44 U.S.C. 3561-3583). In accordance with CIPSEA, every NCHS employee, contractor, and agent has taken an oath and is subject to a jail term of up to five years, a fine of up to $250,000, or both if he or she willfully discloses ANY identifiable information about your hospital or your patients.


HIPAA Privacy Rule and NHAMCS

This section contains an overview of the Privacy Rule and how it affects your NHAMCS participation.  For more comprehensive information on the Privacy Rule and the NHAMCS, please go to HIPAA Privacy Rule Questions and Answers for NHAMCS.

The final Privacy Rule has been published as required by the Health Insurance Portability and Accountability Act of 1996  (HIPAA). Health care providers who transmit financial and administrative health information electronically have been required to comply with the Rule since April 14, 2003.

The Privacy Rule permits your facility to make disclosures of protected health information without patient authorization for public health purposes or for surveillance that has been approved by an NCHS Ethics Review Board (ERB). This survey meets both of these criteria. If you have questions about your facility’s rights as a respondent, you may call the ERB at 1-800-223-8118. The ERB is an independent board that protects the interests of people who take part in studies. Click here to see the ERB approval letter [PDF – 106 KB] for NHAMCS.

We have included all the information you need to be assured that your facility is allowed to disclose protected health information for NHAMCS in our introductory letters [PDF – 276 KB] to hospitals and also here at our website. However, there are several things that you must do to ensure compliance with the Rule when participating in the survey. First, the privacy notice that your facility generally provides to patients must indicate that patient information may be disclosed for either research or public health purposes. And, secondly, your facility may need to keep a record of the disclosure. To assist with this, your hospital will be provided with a document [PDF – 720 KB] that shows that some data from the patient’s medical record were disclosed to CDC for NHAMCS. Of course, if your facility does not transmit health information electronically (such as claims data), then it is not subject to the Privacy Rule or the requirements described above.

The Privacy Rule applies to data collected for NHAMCS because we are asking you to provide certain information about patients without their authorization. For public health and research purposes, NHAMCS collects information from the patient’s medical record such as visit date, birth date, and residential ZIP code. While not directly identifiable, these data are considered protected health information as defined by the Privacy Rule. As described above, the Rule allows you to disclose this information for public health and research purposes.

For additional information on the confidentiality of NHAMCS data, please go to NCHS’s Privacy Protection page and “Frequently Asked Questions (FAQ’s)” about NHAMCS.


Data Utilization

How are NHAMCS data used?

NHAMCS data are currently used to provide statistics that describe the characteristics of visits to hospital emergency departments throughout the United States. The data collected from NHAMCS include patient demographic characteristics; the conditions most often treated; and the diagnostic and therapeutic services rendered, including medication prescribed. These data are used by the U.S. Congress and other public health policy makers, government agencies, universities and medical schools, professional associations, health services researchers and epidemiologists, as well as the print, broadcast, and web media to describe and understand  changes that occur in hospital-based medical care settings. The data are disseminated in the form of government reports, journal articles, web tables and microdata files.

NHAMCS data in the news

NHAMCS survey results and products

NCHS publishes several web tables, reports, and factsheets using NHAMCS data. A list of all these available products can be found here.


Professional endorsements

A number of professional organizations have formally endorsed NHAMCS, including:

  • American College of Emergency Physicians
  • American Health Information Management Association
  • Emergency Nurses Association


Please note, no NHAMCS supplements are being fielded at this time.

Past NHAMCS Data Supplements from Previous Years

The following supplement was used from 2006-2010:

  • Cervical Cancer Screening Supplement [PDF – 138 KB] In 2006, CDC’s National Center for Health Statistics and National Center for Chronic Disease Prevention and Health Promotion joined forces to collect information on the screening of cervical cancer at hospital-based outpatient departments in the United States.Genital human papillomavirus (HPV) infection is common among sexually active populations.  At the start of the supplement, there was considerable new information about HPV infection, transmission, and methods of prevention. In addition, a new DNA test to detect HPV as well as newly approved indications for HPV testing were seen as having important implications for clinicians in both their cervical cancer screening practices and their management of positive HPV diagnoses among female patients and their sex partners. There was recognition that this new information might require different approaches to cervical cancer screening in primary care practice, as well as new information that needed to be conveyed when counseling and educating patients and their sex partners.The Cervical Cancer Screening Supplement was a self-administered 4-page questionnaire given to medical directors of general medicine and obstetric-gynecology clinics that performed cervical cancer screening.  The content included questions about screening methods for cervical cancer, including ordering HPV DNA tests, and administration of the HPV vaccine.

The following supplement was used in 2008:

  • Pandemic and Emergency Response Preparedness Supplement [PDF – 283 KB] The Pandemic and Emergency Response Preparedness Supplement was added to the 2008 NHAMCS at the request of the Office of the Assistant Secretary for Planning and Evaluation (OASPE) of the Department of Health and Human Services (DHHS). Information was obtained on the content of the hospital’s emergency response plan, staff training, participation in mass casualty drills, and the hospital’s resources and capabilities. The questionnaire was adapted from a previous NHAMCS supplement on Bioterrorism and Mass Casualty Preparedness that was fielded in 2003 and 2004. Certain elements (such as existence of updated emergency response plans) remained the same to study trends over time. Other elements were revised to answer questions generated by the previous surveys and newer public health priorities. This project supports the DHHS goal to prepare for emerging health threats.

The following supplement was used in 2002, 2003, and 2006:

  • Emergency Pediatric Services and Equipment Supplement (EPSES) [PDF – 576 KB] The Emergency Pediatric Services and Equipment Supplement (EPSES) was first used in 2002 and 2003 and reintroduced in 2006. It was sponsored by the Health Resources and Services Administration (HRSA) and assessed how well hospitals were prepared to provide emergency pediatric services. NCHS used the data collected to evaluate emergency pediatric preparedness at a national level. This was NOT an assessment or evaluation of individual hospitals. This was a study to produce data for national statistics on pediatric preparedness in hospital ED settings.

The following four supplements were used in 2003 and 2004.

  • Hospital Capacity Card [PDF – 334 KB]
    Because hospital personnel frequently report that the chief reason for ED crowding is the lack of inpatient beds, it is important to obtain inpatient bed counts.  Comparing the number of licensed and staffed beds on the Hospital Capacity Card provided an indication of untapped capacity.
  • ED Staffing and Capacity and Ambulance Diversion (SCAD) Supplement [PDF – 566 KB]
    The purpose of this supplement was to obtain data on issues related to ED crowding.  It is important to know if the ED performs triage, how many treatment spaces there are, specific information about physician staffing, and the availability of on-call specialists.
  • ESA Ambulance Diversion Log [PDF – 1.8 MB]
    The purpose of the Ambulance Diversion Log is to obtain data on ambulance diversion.  There are no national estimates available on diversion frequency and no information comparing types of cases seen in EDs while they are on diversion.
  • Bioterrorism and Mass Casualty Preparedness [PDF – 645 KB]
    One of the biggest obstacles to a hospital’s readiness is recognizing the early signs of a terrorism-related condition, because many biochemical agents trigger routine symptoms in patients.  This was a self-administered two-page questionnaire pertaining to a hospital’s preparedness for events involving bioterrorism and mass casualties.  It included questions on additional training received on this topic since September 11, 2001.