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NCHS

About the National Survey of Ambulatory Surgery

What is the National Survey of Ambulatory Surgery?

The National Survey of Ambulatory Surgery (NSAS) is the only national study of ambulatory surgical care in hospital-based and freestanding ambulatory surgery centers (ASCs). The NSAS was first conducted from 1994 to 1996, but it was discontinued due to lack of resources. The NSAS was conducted again in 2006.

Efforts are now underway to include ambulatory surgery centers in the National Hospital Ambulatory Medical Care Survey (NHAMCS). Hospital-based ASCs were added to the scope of the NHAMCS beginning in 2009, and freestanding ASCs will be added in 2010. The NHAMCS website provides more information on the efforts.

Data for the NSAS was collected for approximately 52,000 ambulatory surgery cases from a nationally representative sample of hospital-based and freestanding ambulatory surgery centers.

These data are used for a variety of planning, administrative and evaluation activities by government, professional, scientific, academic, and commercial institutions, as well as by private citizens.

Changes for 2006

After nearly ten years of being out of the field, the NSAS data collection instruments were updated to reflect the changing environment in ambulatory surgery. Outside experts from the American College of Surgeons, American Association for the Accreditation of Ambulatory Surgery Facilities (AAAASF), American Association of Ambulatory Surgery Centers (AAASC), the American Academy of Ophthalmology (AAO), the American Hospital Association (AHA), the Society for Ambulatory Anesthesiologists (SAMBA), the Federation of American Hospitals (FAH), the Joint Commission of Accreditation of Healthcare Organizations (JCAHO), the Federated Ambulatory Surgery Association (FASA), and the American College of Obstetrics and Gynecology (ACOG) provided input into updating the data collection tools used for NSAS.

Added to the 2006 NSAS were additional questions about the facility in which the ambulatory surgery was provided.

Data Utilization and Dissemination

How are NSAS data used?

NSAS data are used to provide statistics that describe the characteristics of ambulatory surgical visits to hospital-based and freestanding ambulatory surgery centers. These include

  • patient demographic characteristics
  • source of payment
  • information on anesthesia given
  • diagnoses
  • surgical and non-surgical procedures of patients visiting hospital-based and freestanding ambulatory surgery centers.

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 and broadcast media, to describe and understand the changes that occur in medical care. The data are disseminated in the form of public health reports, journal articles, and microdata files and can be seen in a listing of selected articles using NSAS data [PDF - 408 KB].

How are NSAS data released?

Data for the 2006 NSAS will be released several ways. Summary data from the 2006 NSAS will be available in reports from the National Center for Health Statistics. In addition, reports that combine data on ambulatory surgery and surgery performed on hospital inpatients during 2006 will also be published. Reports on topics of special interest may also be published. Information will also be published in journal articles and in papers presented at professional meetings. As resources permit, special tabulations and analyses will be provided to both public and private data requestors. Published reports on the 1994-1996 NSAS are viewable from the site.

In addition to published reports on NSAS, a public-use micro data file and supporting documentation will be prepared for distribution at professional society meetings, health data conferences, and through the NCHS website. NSAS data will also available on CD-ROM. Identification of facilities and patients cannot be made from the public-use data files.

Annual public use files containing information collected by the NSAS were made available for the 1994-1996 NSAS and will be made available for the 2006 NSAS. To facilitate trend analyses, multi-year public use files of NSAS data in a standard format with standard definitions across survey years was and will be made available. CD-ROMs for 1994-1996 in ASCII format are currently available to the public, and 2006 NSAS data will also be available in this format.

To NSAS 2006 Data Users:

The 2006 National Survey of Ambulatory Surgery (NSAS) public use data set was revised in April 2010 to correct an error in the calculation of the AGEINYRS variable for children under 1 year of age. The days and months of these children were incorrectly counted as years in the previously released public use NSAS file. This problem affected about 500 of the approximately 52,000 unweighted records in NSAS, and resulted in children under 1 year of age being misclassified into older age groups. This mistake was discovered when the age distribution obtained using the AGEINYRS variable was different from the one obtained using the AGER10 variable. We advise anyone who has used the AGEINYRS variable in analyses of NSAS 2006 data to rerun these analyses using the revised data set before reporting or publishing any 2006 NSAS data. The posted NSAS Documentation dated May 2009 is unchanged but the data user should note that the data set referred to as NSAS06REV0509.TXT in the documentation is now NSAS06REV0410.TXT. The NSAS06revreadme.txt document has been revised to include the new data set.

April 30, 2010

To NSAS 2006 Data Users:

The revised 2006 National Survey of Ambulatory Surgery (NSAS) public use data set is now available for downloading from our website. The revised public use file documentation is also available. We advise anyone who has used the earlier NSAS data set (released in October 2008) to re-run all analyses using the revised data set before reporting or publishing any 2006 NSAS data. The National Health Statistics Report Number 11, entitled "Ambulatory Surgery in the United States, 2006," [PDF - 468 KB]) has been revised and is now available. The reasons for the revision of the NSAS data set, which affected some of the procedure estimates, are discussed at the beginning of the public use file documentation and in the report. The report also explains that some other estimates of standard errors were printed incorrectly in the original report and these have been corrected. Estimates from the original report should not be used.

Updated September 9, 2009

Professional Endorsements

"I can’t think of a more important way for an ASC professional to spend [their] time. In the face of increasing legislative and regulatory challenges to our industry, our ability to produce the kind of data this survey is collecting is growing. When you participate in surveys such as this one, you help the whole ASC industry as well as your own ASC." -- Jack Egnatinsky, MD, President, Federated Ambulatory Surgery Association (FASA)

The article on NSAS that appeared in the January/February 2006 issue of FASA Update [PDF - 98 KB] is available.

NSAS is endorsed by the following professional organizations:

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