Exploring the Predictors of Post-Clerkship USMLE Step 1 Scores

Theory: We used two theoretical frameworks for this study: a) experiential learning, whereby learners construct new knowledge based on prior experience, and learning grows out of a continuous process of reconstructing experience, and b) deliberate practice, whereby the use of testing (test-enhanced learning) promotes learning and produces better long-term retention. Hypothesis: We hypothesized that moving the USMLE Step 1 exam to follow the clerkship year would provide students with a context for basic science learning that may enhance exam performance. We also hypothesized that examination performance variables, specifically National Board of Medical Examiners (NBME) Customized Basic Science Examinations and NBME subject examinations in clinical disciplines would account for a moderate to large amount of the variance in Step 1 scores. Thus we examined predictors of USMLE Step 1 scores when taken after the core clerkship year. Method: In 2011, we revised our medical school curriculum and moved the timing of Step 1 to follow the clerkship year. We performed descriptive statistics, an ANCOVA to compare Step 1 mean scores for three graduating classes of medical students before and after the curriculum changes, and stepwise linear regression to investigate the association between independent variables and the primary outcome measure after curriculum changes. Results: 993 students took the Step 1 exam, which included graduating classes before (2012-2014, N = 491) and after (2015-2017, N = 502) the curriculum change. Step 1 scores increased significantly following curricular revision (mean 218, SD 18.2, vs. 228, SD 16.7, p < 0.01) after controlling for MCAT and undergraduate GPA. Overall, 66.4% of the variance in Step 1 scores after the clerkship year was explained by: the mean score on fourteen pre-clerkship customized NBME exams (p < 0.01, 57.0% R²); performance on the surgery NBME subject exam (p < 0.01, 3.0% R²); the pediatrics NBME subject exam (p < 0.01, 2.0% R²); the Comprehensive Basic Science Self-Assessment (p <.01, 2.0% R²); the internal medicine NBME subject exam (p < 0.01, 0.03% R²), pre-clerkship Integrated Clinical Skills score (p < 0.01, 0.05% R²), and the pre-matriculation MCAT (p < 0.01, 0.01% R²). Conclusion: In our institution, nearly two-thirds of the variance in performance on Step 1 taken after the clerkship year was explained mainly by pre-clerkship variables, with a smaller contribution emanating from clerkship measures. Further study is needed to uncover the specific aspects of the clerkship experience that might contribute to success on high stakes licensing exam performance.