Which NBME Form should you Use for USMLE Step 1?
This is one of the most common question that I usually encounter both in my blogs and in the various forums. And you have as many answers as there are NBME forms, in fact more. Various answers include the following
- Use all 7 NBME forms to track your progress
- Use at least 2 NBME forms and get the average
- Use NBME form 5 to 7 as they are harder
- Use NBME form 1 to 4 as they are easier
- Use NBME form (#) as they are most predictive
As you can see recommendations vary and reasons vary. My recommendation is to use at least 2 NBME forms, one from the easy set of NBME form 1 to 4 and the second one from the harder set of NBME form 5 to 7 and then get the average. If you want to know why, then read on.
What You Need to Know About the NBME Self Assessment Forms
In order to determine what NBME form you should use, you need to answer 2 questions.
- What is the main purpose of using NBME self assessment tests for USMLE Step 1 Prep?
- What is the difference between the various NBME forms if any?
For this discussion it is important for you to know the following,
- The NBME question pool is different from the USMLE question pool and therefore the style of the questions are different although the content that they are testing is the same.
- USMLE questions are more similar in style with the online qbanks than NBME.
- The basis for using NBME self assessment tests to predict your probable USMLE score is due to the extensive correlation which NBME has done between both test results
- Therefore, the best use of NBME self assessment test is to predict your probable USMLE score and decide the optimum time to take the exam
- Although NBME self assessment tests can be use to assess your progress, there is some limitations. It measures your knowledge of USMLE content but it fails to detect any problem you have answering USMLE type questions.
What are the Difference in Difficulty Levels of the Various NBME Forms
There are differences in the difficulty level of the different NBME forms. The higher the NBME form number, the more difficult the questions. Therefore, NBME form 1 is the easiest while NBME form 7 is the toughest.
However, since all 7 NBME forms are normed and correlated to the same USMLE exam, the predictability of all 7 sets are fairly similar but not exact. In other words, even if the NBME form 7 is tougher than the other exam, the number of correct questions you need to get an equivalent score in the USMLE is actually lower.
I have also observed that the lower NBME forms tend to overestimate your actual USMLE score a little, while the higher NBME forms tend to underestimate your actual USMLE scores a little. But overall, they are still within the SD level of + or – 11 points on the 3 digit score.
So What is the Best NBME Form to Take for USMLE Step 1?
If the purpose is to predict the probable score you will get if you were to sit for the USMLE, then my recommendation will be to take two NBME forms and get the average score. One NBME form from the easy group Forms 1 to 4 and the second one for the harder group of NBME Forms 5 to 7.
If you only have the financial resource to take 1 form then either NBME form 4 or 5 will be a good choice as they are of intermediate difficulty.
What you should not do of course is to take the “downloaded” or “pdf” version as aside from issues of copyright, it is the predicted USMLE score that is important and not the actual percentage of correct answers you got.
If the purpose is to assess the progress of your USMLE Step 1 review, then my recommendation is not to use the NBME forms at all but use 4 blocks of UW or Kaplan Qbanks on a random, timed, mixed unused basis.