NBME CBSE and CCSE: What They Are and How to Read Your Score

Short answer: the CBSE (Comprehensive Basic Science Examination) and CCSE (Comprehensive Clinical Science Examination) are NBME subject exams that schools and other programs administer under proctored conditions. The CBSE mirrors Step 1 and reports an equated percent correct score with an estimated probability of passing Step 1. The CCSE mirrors Step 2 CK and reports a score on the same 1–300 scale as Step 2 CK.

CBSE vs CCSE at a glance

Is the CBSE the same as an NBME practice test?

Not quite. The CBSE and CCSE are subject exams that an institution orders and proctors, either at the school or at a Prometric test center, and NBME says they are not meant for practice use. The versions you buy on your own are the self-assessments: CBSSA for Step 1 and CCSSA for Step 2 CK. Both pairs use the same score-reporting approach, so the guidance below applies to either.

How the CBSE is scored now

Your report gives a total equated percent correct (EPC) score. NBME describes it as the percentage of the content you have mastered, adjusted for small differences in form difficulty, so it can sit slightly above or below the raw share of questions you got right. The report also shows a likely score range of about 4 points either way, the Step 1 low-pass range, and your estimated probability of passing Step 1 if you test within a week.

Is there a CBSE score conversion to Step 1?

Not anymore. Before 2022 the CBSE reported a three-digit score meant to estimate Step 1 performance, which is where the CBSE conversion and equivalency charts still circulating online come from. When Step 1 moved to pass/fail on January 26, 2022, NBME replaced the CBSE three-digit score with the equated percent correct score; the new reports were planned for February 23, 2022. A three-digit number made from a current CBSE score is an unofficial estimate of a score Step 1 no longer reports.

What replaces the conversion is the comparison NBME prints on the report. Look at where your likely score range sits against the Step 1 low-pass range:

NBME adds that results are most useful when you test under Step-like conditions, in one sitting and without resources, and that two or more results in the borderline-to-above zone are more reassuring than one. To check a CBSSA percent against the same low-pass logic, use the NBME Step 1 score conversion; for a CBSE, read the low-pass range printed on your own report.

How the CCSE is scored

The CCSE needs no conversion: NBME reports it on the same 1–300 scale as Step 2 CK, as an estimate of how you would have scored on Step 2 CK with the same knowledge and conditions. The likely score range is about 8 points either way, and the report shows the Step 2 CK low-pass range and an estimated probability of passing within a week, read with the same four scenarios as the CBSE.

If you also have CCSSA forms, the NBME score conversion covers each form, and the Step 2 CK percentile calculator shows where a score at that level ranks in the official USMLE norm table.

What the CBSE and CCSE cover

NBME says the CBSE covers material typically learned in the basic science years, with somewhat more weight on second-year courses, and reflects Step 1 content using the same item formats. Its system ranges match the Step 1 outline, led by reproductive and endocrine (12–16%), respiratory and renal (11–15%), and behavioral health and nervous systems (10–14%). By physician task, 60–70% of questions test applying foundational science concepts.

The CCSE covers material from the core clinical clerkships and reflects Step 2 CK content. Most systems carry 5–10% each, social sciences including ethics and patient safety carry 10–15%, and by physician task the exam splits mostly between diagnosis (40–50%) and pharmacotherapy, intervention, and management (40–50%), with health maintenance at 10–20%.

The CBSE for dental applicants (OMS and dental anesthesiology)

The CBSE is also used outside medical school. AAOMS registers dental students for the CBSE as part of applying to oral and maxillofacial surgery programs; its FAQ describes 200 multiple-choice questions in four 60-minute sections within a 4-hour, 15-minute session (NBME's own timing chart lists 5 hours 15 minutes, so confirm the length on your scheduling permit), says you may take it as many times as you wish, and says scores stay valid for several years unless AAOMS states otherwise. ASDA offers the CBSE to dental anesthesiology applicants in two Prometric windows each year, February 1–14 and July 1–14.

One mismatch to know about: the AAOMS FAQ still says a table of approximate Step 1 equivalents comes with the score report, while NBME's current CBSE documentation describes the equated percent correct format. Go by the report you actually receive, and ask AAOMS or your target programs which number they review.

Quick answers

• Is the CBSE harder than Step 1? NBME does not compare difficulty. The CBSE follows the Step 1 content outline and item formats, and scores are equated across forms.
• What is a good CBSE score? For Step 1 readiness, a likely score range completely above the low-pass range on your report. For dental residency applications, ask each program.
• Can I take the CBSE on my own? For medical students the CBSE is ordered by the school; the self-purchase version is the CBSSA. Dental applicants register through AAOMS or ASDA.
• Does CCSE need converting to a Step 2 CK score? No. It already uses the 1–300 Step 2 CK scale.