Abstract
BACKGROUND: Variation in physicians' practice patterns contributes to unnecessary health care spending, yet the influences of modifiable determinants on practice patterns are not known. Identifying these mutable factors could reduce unnecessary testing and decrease variation in clinical practice. OBJECTIVE: To assess the importance of the residency program relative to physician personality traits in explaining variations in practice intensity (PI), the likelihood of ordering tests and treatments, and in the certainty of their intention to order. METHODS: We surveyed 690 interns and residents from 7 internal medicine residency programs, ranging from small community-based programs to large university residency programs. The surveys consisted of clinical vignettes designed to gauge respondents' preferences for aggressive clinical care, and questions assessing respondents' personality traits. The primary outcome was the participant-level mean response to 23 vignettes as a measure of PI. The secondary outcome was a certainty score (CS) constructed as the proportion of vignettes for which a respondent selected "definitely" versus "probably." RESULTS: A total of 325 interns and residents responded to the survey (47% response rate). Measures of personality traits, subjective norms, demographics, and residency program indicators collectively explained 27.3% of PI variation. Residency program identity was the largest contributor. No personality traits were significantly independently associated with higher PI. The same collection of factors explained 17.1% of CS variation. Here, personality traits were responsible for 63.6% of the explained variation. CONCLUSIONS: Residency program affiliations explained more of the variation in PI than demographic characteristics, personality traits, or subjective norms.