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.