The national ambulatory medical care survey (NAMCS) at fifty: Past and future

NAMCS, sponsored by the Centers for Disease Control and Prevention, is an annual nationally representative sample survey of visits to non-federal office-based physicians, excluding anesthesiologists, radiologists, and pathologists. NAMCS has collected physician-reported ambulatory care encounter-specific content over five decades. We assessed trends in the use of the data by the health services research community, response rates, and questionnaire changes.

We extracted all peer-reviewed journal articles using NAMCS data published between 1973 and 2020 and categorized publications into high- and low-impact groups, with high impact considered as the top 25 % of journals. We then examined the annual number of journal publications using NAMCS, data according to the year collected, by impact score groups for 50 years. We compared response rates and the information requested by NAMCS questionnaires from 1973 to the present.

There has been a significant decline in the overall use of NAMCS data by the non-federal health services research community for publication in both high and lower-impact journals. Data used for high impact publications peaked in 1998, at 87, remained high at 58 in 2008 but then sharply declined. Concurrently, there was a substantial decline in NAMCS survey response rates (highest: 80.5 % in 1975 vs. lowest: 28.8 % in 2015). These changes came in the context of increasing questionnaire complexity.

Over the last two decades, annual publication rates citing NAMCS data have declined, coincident with lower response rates and more detailed questionnaires. Nationally representative encounter-specific data verified by the clinician of record will likely have renewed value for those who develop, implement, and assess healthcare policy if response rates improve, and questionnaire review and finalization are streamlined. Though multispecialty data offer unique opportunities for comparisons, sampling a subset of clinicians, such as those providing primary care, would complement national efforts to improve access to continuous comprehensive care.