Reliability and Validity of Conversion Formulas Between Comprehensive Osteopathic Medical Licensing Examination of the United States Level 1 and United States Medical Licensing Examination Step 1

Abstract

Abstract Background The Comprehensive Osteopathic Medical Licensing Examination of the United States (COMLEX-USA) Level 1 and United States Medical Licensing Examination (USMLE) Step 1 scores are important factors in the selection process of medical students into US residency programs. Objectives The goals of this study were to investigate the correlation between the COMLEX-USA Level 1 and the USMLE Step 1 and to assess the accuracy of the existing formulas in predicting USMLE scores from COMLEX-USA scores. Methods A retrospective study of 1016 paired COMLEX-USA Level 1 and USMLE Step 1 scores was conducted. Formulas by Sarko et al and by Slocum and Louder were used to estimate USMLE Step 1 scores from COMLEX-USA Level 1 scores, and a paired t test between calculated USMLE Step 1 scores and actual USMLE Step 1 scores was performed. Results During 2006–2012, 1016 of 1440 students (71%) took both the USMLE Step 1 and the COMLEX-USA Level 1 tests in the College of Osteopathic Medicine of the Pacific. The USMLE Step 1 scores were higher than those predicted by Slocum and Louder and by Sarko et al by an average of 14.16 ± 11.69 (P < .001) and 7.80 ± 12.48 (P < .001), respectively. A Pearson coefficient of 0.83 was observed. Regression analysis yielded the following formula: USMLE Step 1  =  0.2392 × COMLEX-USA Level 1 + 82.563 (R2  =  0.69577). Conclusions The USMLE Step 1 scores, on average, were higher than those predicted by the formulas derived by Slocum and Louder and by Sarko et al. Residency program directors should use caution when using formulas to derive USMLE Step 1 scores from COMLEX-USA Level 1 scores.