Why RX is What You Need

From the authors of First Aid

First Aid is the #1 trusted resource for medical students, from classroom to clerkships and beyond. Our authors are medical students who know what’s tested on the USMLE, who can organize information efficiently, and who share their experiences with you. For medical students, by medical students – First Aid and USMLE-Rx are all about building a strong medical community.

All the Facts at your fingertips

Our Step 1 Qmax and Flash Cards are the ONLY test prep tools that link directly to Facts in the First Aid book. We think your time is precious, and we give you the Facts on-screen so you can review them immediately when you need them.

100% pass guarantee

If you fail the USMLE while using the USMLE-Rx product that corresponds to that test, you may be eligible to extend your USMLE-Rx subscription. If you qualify, you will receive a subscription extension to the same USMLE-Rx product equal in length to your original USMLE-Rx subscription. Limit one extension per paid subscription. For more details, see Terms and Conditions.

Predictive of actual USMLE performance

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, 26 U.S. medical students who used USMLE-Rx Step 1 Qmax for USMLE preparation completed baseline questionnaires regarding their performance on USMLE-Rx, Kaplan Qbank 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: See table below. Participants had higher than average scores for the USMLE Step 1, MCAT, and USMLE-Rx Step 1 Qmax. USMLE-Rx scores strongly correlated with USMLE scores. Kaplan and MCAT scores had moderate correlation. In single linear regression modeling, USMLE-Rx Step 1 Qmax, Kaplan Qbank and MCAT scores were highly significant predictors of USMLE performance with high T-scores. USMLE-Rx Step 1 Qmax scores were able to account almost 80% of the variance in USMLE scores.



Mean score (SD)

Correlation (Rho)



Variance (R2)

USMLERx Step 1 Qmax

68.9 ±7.7





Kaplan Qbank







31.7 ±0.5





USMLE (3-digit)

234.7 ±19.8





Conclusions: USMLE-Rx Step 1 Qmax, Kaplan Qbank and MCAT scores appear to be significant predictors of USMLE performance. In this sample, USMLE-Rx was highly correlated with the USMLE Step 1 performance and was able to predict approximately 80% of the variation in USMLE scores.

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)