Background: Health services research has documented the magnitude of health care variations. Few studies focus on provider level sources of variation in clinical decision making-for example, which primary care providers are likely to follow clinical guidelines, with which types of patient.
Objectives: To estimate: (1) the extent of primary care provider adherence to practice guidelines and the unconfounded influence of (2) patient attributes and (3) physician characteristics on adherence with clinical practice guidelines.
Design: In a factorial experiment, primary care providers were shown clinically authentic video vignettes with actors portrayed different "patients" with identical signs of coronary heart disease (CHD). Different types of providers were asked how they would manage the different "patients" with identical CHD symptoms. Measures were taken to protect external validity.
Results: Adherence to some guidelines is high (over 50% of physicians would follow a third of the recommended actions), yet there is low adherence to many of them (less than 20% would follow another third). Female patients are less likely than males to receive 4 of 5 types of physical examination (p < .03); older patients are less likely to be advised to stop smoking (p < .03). Race and SES of patients had no effect on provider adherence to guidelines. A physicians' level of experience (age) appears to be important with certain patients.
Conclusions: Physician adherence with guidelines varies with different types of "patient" and with the length of clinical experience. With this evidence it is possible to appropriately target interventions to reduce health care variations by improving physician adherence with clinical guidelines.