Relationship between students' performances on the NBME Comprehensive Basic Science Examination and the USMLE Step 1: a longitudinal investigation at one school.

PURPOSE: To examine students' growth in basic science knowledge during medical school and to evaluate the accuracy of students' scores on the National Board of Medical Examiners Comprehensive Basic Science Subject Examination (CBSE) as predictors of their performances on Step 1 of the United States Medical Licensing Examination (USMLE). METHOD: A public medical school in the southwestern United States evaluated 58 students from the entering class of 1993 by administering the CBSE in April 1994, December 1994, and February 1996. These students then sat for the USMLE Step 1 in June 1996. For each CBSE administration, descriptive statistics were calculated and least-squares regression analyses were performed to predict the students' Step 1 scores from their CBSE scores. RESULTS: The students' CBSE scores improved as they progressed through their basic science course work and clinical clerkships. The strongest correlation (r = .85) between the students' CBSE scores and their Step 1 scores was for the second CBSE administration; the weakest correlation (r = .73) was for the first CBSE administration. CONCLUSION: These results indicate that basic science knowledge continues to grow throughout the first three years of medical school and that the CBSE is a useful tool for the identification of students at risk for failing the USMLE Step 1.