Objectives: The authors studied the consistency of performance of individual physicians to evaluate the identification of outlier practitioners as a strategy for improving patient care.
Methods: The authors used a data base containing information on 430 practitioners caring for 6,090 patients in 16 group practices. The authors analyzed inter- and intraphysician differences in performance on the basis of review criteria for 8 patient care guidelines. These criteria allowed for a variety of acceptable clinical strategies, incorporated decision tree logic, and included input from participating practitioners. The authors took steps to maximize validity and controlled for potentially confounding characteristics of patients and practitioners. The authors identified outliers, evaluated the significance of differences between outliers and nonoutliers, and studied variations in performance across cases and guidelines in conformance with guidelines.
Results: The authors identified a few statistically significant outliers. Correlations for performance across cases seen by a given physician were low. The highest positive correlation for performance between any pair of guidelines was 0.32.
Conclusions: The performance of a given practitioner is highly variable from patient to patient and from guideline to guideline. Thus, strategies focusing solely on substandard outliers will miss opportunities to improve performance.