USMLE-Rx Predicts USMLE Step 1 Performance

Rationale: Medical students have few validated predictors of USMLE performance. We hypothesized that USMLE-Rx Step 1 Qmax could predict USMLE Step 1 performance.

 

 

Methods: In this prospective cohort study, 97 U.S. medical students who used USMLE-Rx Step 1 Qmax for USMLE preparation completed baseline questionnaires regarding their undergraduate GPA along with their performance on USMLE-Rx and the Medical College Admissions Test (MCAT). All questionnaires were completed within one week of participants taking their Step 1 examination. Participants subsequently reported their 3-digit USMLE Step 1 scores when they became available. Spearman’s rho and single linear regression modeling were used to assess associations between variables.

Results: Qmax survey respondents answered an average of 1075 questions (min 20, max 4030) and answered 66% correctly (min 16%, max 94%). The above graph pictures a scatter plot of USMLE scores by the percentage of correct answers. The 95% Confidence Interval represents the confidence in the underlying true average USMLE score for each value of Percentage of Correct Answers. The 85% Tolerance Interval indicates that there is a 95% certainty that 85% of future values would fall in this interval.

Conclusions: After adjusting for known predictors of the USMLE Step 1 score (MCAT score and undergraduate GPA), the Qmax Percentage of Correct Answers was a significant independent predictor, p<.001.  For every 10% increase in the Qmax Percentage of Correct Answers, a student is predicted to improve their USMLE Step 1 score by 8.40 points.

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You can also use the following formula:
USMLE-Rx Step Qmax(%)*2.64 + 47 = USMLE Step 1 3-digit score (+/- 20 for the 95% CI)