A cross-sectional study of the practice types of US adult primary care physician specialists

Background Many physicians listed as primary care in databases such as the American Medical Association (AMA) Masterfile do not provide traditional ambulatory primary care. Objective To compare physicians listed in the AMA Masterfile as primary care physician (PCPs) specialists for adult patients with their actual practice type. Methods We conducted a cross-sectional study of the AMA Masterfile report for PCPs who care for adults (listed as family medicine, internal medicine, medicine-paediatrics, and geriatrics) in the summer and fall of 2018 (spring of 2019 for Hartford, CT) in the primary counties of 8 metropolitan areas across the United States. We searched multiple websites to determine the actual practice type of each physician in the study counties. We correlated the 2 datasets: the AMA Masterfile list vs the results of our searches. Results Family physicians were more likely to function as traditional ambulatory PCPs than internists [1,738/2,101 (82.7%) vs 1,241/2,025 (60.9%), P < 0.001], and less likely to be hospitalists [83/2,101 (4.0%) vs 631/2,025 (31.0%), P < 0.001]. Other practice types included urgent care [105 (5.0%) family physicians, 16 (0.8%) internists] and emergency medicine [49 (2.3%) family physicians, 20 (1.0%) internists]. The AMA Masterfile identified 4,892 practicing PCPs for adult patients in the study counties, of which 3,084 (63.0%) matched by location and ambulatory PCP practice type [3,695 (75.5%) for ambulatory PCP practice type only]. Conclusions We provide an updated estimate using a unique methodology to estimate how to correct the AMA Masterfile for PCPs who actually provide traditional ambulatory primary care to adult patients.