COMLEX Level 1 to USMLE Step 1 Predictor

How Your COMLEX Level 1 Score Predicts Your USMLE Step 1 Percentile

D.O. students will take the Comprehensive Osteopathic Medical Licensing Examination (COMLEX) of the United States on their way to becoming a doctor. When applying for residency, many D.O. students will apply to programs that are accredited by either the American Osteopathic Association (AOA) or the Accreditation Council for Graduate Medical Education (ACGME). Previously, D.O. students could apply to either AOA or ACGME programs, and M.D. students could only apply to ACGME programs. While both D.O. and M.D. students will be able to apply to both AOA and ACGME programs under the upcoming AOA and ACGME merger, most ACGME residency program directors prefer that D.O. applicants also take the United States Medical Licensing Examination (USMLE) as they are more familiar with this test.

Students who have taken the COMLEX Level 1 may wonder how they can use this score to predict their USMLE Step 1 score or Step 1 percentile. While the administrators of the COMLEX are currently developing a study plan for the development of a valid and reliable conversion formula of the COMLEX Level 1 score to the USMLE Step 1 score, we at Elite Medical Prep did a survey of the literature to help you all answer this question.

Background on COMLEX Level 1 and USMLE Step 1 Scores

The minimum COMLEX Level 1 passing score is currently 400 with, as of students who took the exam between May 2018 and April 2019, the 25th comlex percentile score at ~465, 50th percentile score at ~525, and 75% at ~587. The minimum USMLE Step 1 passing score is currently 194 with the 25th step 1 percentile score at ~215, 50th percentile score at ~230, and 75% at ~245. 

Current Data on Converting between the COMLEX Level 1 Score and USMLE Step 1 Score

While there is no formal conversion between the COMLEX Level 1 and USMLE Step 1 Score there is published that COMLEX Level 1 scores and USMLE Step 1 scores are highly correlated (Figure 1.) (Chick et al., Teaching and Learning in Medicine, 2010 and Sandella et al., Journal of Graduate Medical Education, 2016 and Kane et al., The Journal Of Emergency Medicine, 2016).

However, in 2006, Philip Slocum, DO and Janet Louder published a paper titled “How to Predict USMLE Scores from COMLEX-USA Scores: A Guide for Directors of ACGME-Accredited Residency Programs” in the Journal of the American Osteopathic Association. In this paper, they looked at 155 students at a single medical school who took both the COMLEX Level 1 and USMLE Step 1 and concluded the following:

• There was a statistically significant correlation between COMLEX Level 1 Scores and USMLE Step 1 Scores
• One can estimate the USMLE Step 1 Score from the COMLEX Level 1 score with the following equation:
  • USMLE Step 1 Score = 67.97 + 0.24 X COMLEX LEvel 1 Score (R2=0.68)

However, there are several critical limitations to this study that we need to emphasize

• The sample size is extremely small when considering that thousands of students take the COMLEX Level 1 and USMLE Step 1 examinations every year.
• All of the students in this study came from a single institution
• This study was conducted in 2006 possibly making their proposed formula quite inaccurate today
• The coefficient of determination (R2) in their derived formula is only 0.68 which demonstrates that this formula is by no means accurate. The R2 explains the extent to which the variance of one variable explains the variance of the second variable. So in this paper, more than half of the observed variation in the predicted USMLE Step 1 score can be explained by a student’s COMLEX Level 1 Score.

Conclusions

We at Elite Medical Prep believe that there are no great models that predict your USMLE Step 1 Score based off of your COMLEX Level 1 Score. Most papers published on this subject are limited by the fact that they generally utilize a very small sample size which comes from a handful of medical schools. Until a much larger data set is utilized, we cannot recommend any “equation” or “score conversion software” to accurately predict your USMLE Step 1 Score from your COMLEX Level 1 Score. Additionally, we could not find any literature demonstrating a conversion of a students COMLEX Level 1 percentile to a USMLE Step 1 percentile – a conversion which of greater utility for both students and residency program directors. We look forward to seeing what the administrators of the COMLEX will develop to convert one’s COMLEX Level 1 score to the USMLE Step 1 score in the near future.

However, we do believe that there is a correlation between the two tests in that students who do well on the COMLEX Level 1 generally tend to also do well on the USMLE Step 1. While this relationship is by no means causative, we recommend that students put forth their full effort when preparing for both examinations. A score on the COMLEX Level 1 in the 90th percentile by no means guarantees your Step 1 percentile will also be in the 90th. However, if you follow good test preparation strategies and work hard, you can succeed on both!

We hope this post was insightful in understanding how your COMLEX Level 1 Score Predicts Your USMLE Step 1 Score (or rather, how it doesn’t). If you are in need of resources to prepare for either Step 1 or Level 1, you can find several study plans and resource reviews on the Elite Medical Prep blog. In addition, if you need more focused help, contact us here to speak with a learning specialist.