Objective: To determine the relative contributions of: (1) patient attributes; (2) provider characteristics; and (3) health care systems to health care disparities in the management of coronary heart disease (CHD) and depression.

Data sources/study setting: Primary experimental data were collected in 2001-2 from 256 randomly sampled primary care providers in the U.S. (Massachusetts) and the U.K. (Surrey, Southeast London, and the West Midlands).

Study design: Two factorial experiments were conducted in which physicians were shown, in random order, two clinically authentic videotapes of "patients" presenting with symptoms strongly suggestive of CHD and depression. "Patient" characteristics (age, gender, race, and socioeconomic status [SES]) were systematically varied, permitting estimation of unconfounded main effects and the interaction of patient, provider, and system-level influences. DATA COLLECTION/DATA EXTRACTION METHODS: Analysis of variance was used to measure provider decision-making outcomes, including diagnosis, information seeking, test ordering, prescribing behavior, lifestyle recommendations, and referrals/follow-ups.

Principal findings: There is a high level of consistency in decision making for CHD and depression between the U.S. and the U.K. Most physicians in both countries correctly identified conditions depicted in the vignettes, although U.S. doctors engage in more information seeking, are more likely to prescribe medications, and are more certain of their diagnoses than their U.K. counterparts. The absence of any national differences in test ordering is consistent for both of the medical conditions depicted. U.K. physicians, however, were more likely than U.S. physicians to make lifestyle recommendations for CHD and to refer those patients to other providers.

Conclusions: Substantively, these findings point to the importance of patient and provider characteristics in understanding between-country differences in clinical decision making. Methodologically, our use of a factorial experiment highlights the potential of these methods for health services research-especially the estimation of the influence of patient attributes, provider characteristics, and between-country differences in the quality of medical care.