—To determine differences in the mix of patients among medical specialties and among organizational systems of care.
—Cross-sectional analysis of 20 158 adults (≥18 years of age) who visited providers' offices during 9-day screening periods in 1986. Patient and physician information was obtained by self-administered, standardized questionnaires.
—Offices of 349 physicians practicing family medicine, internal medicine, endocrinology, and cardiology within health maintenance organizations, large multispecialty groups, and solo or small single-specialty group practices in three major US cities.
—Demographic characteristics, prevalence of chronic disease, disease-specific severity of illness, and functional status and well-being.
—Among patients with selected physician-reported chronic illnesses (diabetes, hypertension, recent myocardial infarction, or congestive heart failure), increasing levels of severity were associated with decreasing levels of functional status and well-being and with increased hospitalizations, more physician visits, and higher numbers of prescription drugs. Compared with patients of general internists, patients of cardiologists were older (56 vs 47 years, P<.01), had worse functional status and well-being scores (P<.01), and carried more chronic diagnoses (mean 1.32 vs 1.02, P<.01); patients of family practitioners were younger (40 vs 47 years, P<.01) and more functional (P<.01), carried fewer chronic diagnoses (0.70 vs 1.02, P<.01), and (among diabetic patients only) had lower disease-specific severity scores (2.06 vs 2.30 on a five-point scale, P<.01). Compared with patients in health maintenance organizations, patients visiting solo practitioners under fee-for-service payment were older (50 vs 45 years, P<.01) and sicker (had worse physical functioning) and had a higher mean number of chronic diagnoses (1.10 vs 0.93, P<.01).
—Patient mix is related to utilization and differs significantly across medical specialties and systems of care. These differences must be taken into account when interpreting variations in utilization and outcomes across specialties and systems, and when considering alternative policies for payment.(JAMA. 1992;267:1617-1623)