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National Hospital Ambulatory Medical Care Survey (NHAMCS)

National Hospital Ambulatory Medical Care Survey (NHAMCS)

The National Hospital Ambulatory Medical Care Survey (NHAMCS) is designed to collect data on the utilization and provision of hospital-based ambulatory care services.

Recently, you may have been asked to respond to the National Hospital Ambulatory Medical Care Survey (NHAMCS). This page provides additional information about the survey, including how to verify the survey is being conducted by the Census Bureau, that the person who contacted you is a Census Bureau employee, what you can expect if you or your facility has been selected to participate in the survey, and how we ensure that the data you provide are protected.

If you have additional concerns that are not addressed on this page, and wish to contact Census Bureau staff regarding the survey, please see the contact information at the bottom of this page.


The National Hospital Ambulatory Medical Care Survey (NHAMCS) is the Nation’s foremost study of ambulatory medical care in hospital emergency departments and has been conducted annually since 1992. Each year, approximately 450 nationally-representative hospitals provide data on a sample of patient visits to their emergency service areas. Sampled data are collected over a designated 4-week reporting period. These data are weighted to produce national estimates that are widely used by health care researchers, policy analysts, congressional staff, the news media, and many others, and have helped to improve our knowledge of ambulatory care patterns in the Nation’s hospitals. NHAMCS is sponsored by the Centers for Disease Control and Prevention’s (CDCs) National Center for Health Statistics (NCHS), and is administered by the U.S. Census Bureau.

Why is this survey important?

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

What is the legal authority for conducting this survey?

NHAMCS is authorized by Title 42, United States Code, Section 306 (242k), which permits data collection for health research. The U.S. Census Bureau is conducting this survey on behalf of the National Center for Health Statistics (NCHS) under the authority of Title 13, United States Code (U.S.C.), Section 8(b). We take your privacy very seriously. All information that relates to or describes identifiable characteristics of individuals 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 USC 242m(d)) and the Confidential Information Protection and Statistical Efficiency Act of 2002 (CIPSEA, Title 5 of Public Law 107-347). The Privacy Rule, as mandated by the Health Insurance Portability and Accountability Act (HIPAA) (Public Law 104-191), allows hospitals to participate in NHAMCS.

What should you expect if your facility was randomly selected to be in the survey?

Hospitals selected for NHAMCS will first receive a letter from the Director of NCHS that provides more information about the survey, and letting the hospital know that they can expect to be contacted by a representative from the Census Bureau in the near future.

How was my facility selected to be in this survey?

The National Center for Health Statistics (NCHS) scientifically selects random hospitals throughout the country to participate in NHAMCS. If your hospital is selected, you will receive a letter from in the Director of NCHS that more information about the survey, and letting the hospital know that they can expect to be contacted by a representative from the Census Bureau in the near future.

How can I verify that my facility was selected for this survey?

If you wish to verify that your facility was selected for this survey, you can contact your Census Bureau Regional Office, and they can verify whether or not your hospital was selected for NHAMCS (see the map for contact information.)

How can I verify that the person contacting me is a Census Bureau employee?

All Census Bureau field representatives identify themselves by name and carry a badge identifying him/her as a U.S. Census Bureau employee. They will be carrying a laptop with the Census Bureau logo on it to conduct the survey.

If you receive a call or visit and wish to verify that the person contacting you is a Census Bureau employee, you can call one of our regional offices or you can use the staff search on our website.

Is participation mandatory?

Participation in NHAMCS is voluntary. However, when you participate, you are representing hundreds of other hospitals in your geographic region and state. In order to be able to create quality statistics, we rely on the participation of those who are randomly selected. If you choose not to participate, your hospital and others like it will not be adequately represented.

Can my patients or I be identified by my responses?

NCHS collects and uses information you provide in accordance with System of Records Notice 09-20-0164, Health and Demographic Surveys Conducted in Probability Samples of the United States. We take your privacy very seriously. We combine your answers with other respondent’s answers in a way that keeps everyone’s identity secret. As required by federal law, your identity can be seen only by those NCHS employees and specially designated agents (such as the U.S. Census Bureau) who need that information for a specific reason. No one else can see your answers until all information that could identify a specific individual has been removed.

Every National Center for Health Statistics (NCHS) employee, contractor, research partner, and agent has taken an oath to keep your information private. Anyone who willfully discloses ANY identifiable information about ANYONE in the survey could get a jail term of up to five years, a fine of up to $250,000, or both. Per the Federal Cybersecurity Enhancement Act of 2015 (6 U.S.C. §§ 151 & 151 note), your data are protected from cybersecurity risks through screening of the systems that transmit your data.

How do I know my responses are safe?

The responses that are collected from surveys conducted by the Census Bureau are encrypted both in transit and at rest on the Census Bureau’s computer servers. These servers are part of a stand-alone network that is not accessible by the Internet. In addition, these servers are constantly monitored for any signs of intrusions.

Where can I find the statistics produced by this survey?

To see examples of reports, tables, and charts that use data from the survey, you can visit NCHS’s website on Ambulatory Medical Care Data.

What if I have additional questions, recommendations, or issues that I need resolved?

If you have additional questions about the survey, or if you wish to speak to someone at the Census Bureau, you can contact the respondent advocate. The respondent advocate can address the concerns of those hospitals that have been selected to participate in this survey, as well as share that feedback with those who manage the survey operations.

The Census Bureau has a web page “Are You In A Survey” designed to answer additional questions you might have about being in a Census survey.

For more Frequently Asked Questions about NHAMCS, please see:

Page Last Revised - October 28, 2021
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