Identifying primary care disciplines by analyzing the diagnostic content of ambulatory care.

BACKGROUND: There is considerable controversy about which medical specialties are primary care disciplines. This paper addresses this issue by examining the extent to which the major physician disciplines provide comprehensive ambulatory care to large segments of the population, a characteristic central to the provision of primary care. METHODS: The study is based on ambulatory visits to office-based physicians recorded in the 1980-81 and 1989-90 versions of the National Ambulatory Medical Care Survey. Each diagnosis is aggregated into one of 120 mutually exclusive diagnostic clusters. A primary care encounter is defined as a nonreferred ambulatory visit for one of the top 20 clusters. RESULTS: Family medicine, general internal medicine, and general pediatrics provide the majority of nonreferred ambulatory care for common conditions in the United States. All three of these disciplines provide a comprehensive range of ambulatory care to large segments of the population. Obstetrician-gynecologists are an important source of care for women of childbearing age, but they tend to limit their care to obstetric and gynecologic problems; most care for adult women is provided by family physicians and general internists. CONCLUSIONS: Although most specialties provide outpatient services to different segments of the population, only the traditional primary care disciplines of family practice, general internal medicine, and general pediatrics provide comprehensive ambulatory care to broad population groups.