The impact of residents, interns, and attendings on inpatient laboratory ordering patterns: a report from one university's hospitalist service.

PURPOSE To examine the laboratory test ordering patterns of interns to determine the effects of more senior residents' and attendings' supervision on trainees' patterns and residents' perceptions of control in test ordering. METHOD In a 2007 cohort study of 2,066 patients cared for by 85 interns, 56 residents, and 27 attendings on the University of Pennsylvania general medical hospitalist service, the authors studied variation in laboratory test utilization and costs in 10,908 patient-days. Ordinary least squares regression was used to partition variance among supervised and supervising physicians. Interns and residents were surveyed about their perceived control over lab test ordering. RESULTS Forty-five percent (95% confidence interval [CI]: 39-53) of the variation in laboratory test utilization was attributable to interns' ordering, 26% (95% CI: 21-34) to residents, and 9% (95% CI: 7-16) to attendings; 20% (95% CI: 6-25) could not be uniquely attributed to a particular level of the care team. Similar results were obtained for variation in laboratory costs. Interns underestimated their control over laboratory test utilization, residents overestimated their control, and both groups had inaccurate assessments of their utilization relative to peers. CONCLUSIONS Attending faculty had relatively little impact on laboratory ordering patterns. This may reflect a consistent baseline impact of attending physicians on laboratory use, but it may also represent a missed opportunity to reduce practice variation and improve patient care. Observing variation in trainee practice patterns in the face of different supervisors represents a new approach to measuring the supervision in clinical settings.