I think MD students probably have more "academic prowess" on average than DO students. Exactly what that means is open to debate. I'm pretty confident that the average MCAT scores shed some light onto standardized test taking skills. There may also be some deeper differences in study habits in general... hell, maybe even inherent IQ. But I'm not convinced that IQ is the biggest predictor of USMLE scores... maybe, maybe not? I'd think it would have a stronger correlation on the higher end of the range, and much less so on the lower end where pass/fail rules. Study and preparation is paramount down there. Not that any of that dictates who will be a "better physician" but I think there is something to the idea that MD students have proven themselves to be stronger testers in the past, whether through undergrad exams, MCAT, or both.
Then there are the content and emphasis differences in the exam. I'm sure more than one DO student has encountered the USMLE not particularly well prepared for the biochem, molecular, or genetics questions. Shame on them.
And finally, there has always been a mentality among a subset of DO students that "I can take the USMLE, see how I do, and report the scores if warranted." While I think that option is much less "legit" than it was in years past, it still exists, dishonest or not. And for some students, it goes further than reporting USMLE scores or not... if they don't do well on the USMLE, they just stick to the osteopathic match. No harm done. Unfortunately, I've heard several students in my own class say something like "I'm studying for the COMLEX and will take the USMLE too just in case I want to apply to allopathic." Preparing for the COMLEX as the primary test IMO isn't the right approach, and probably leads to a few failures.
If we had the distribution of scores for DO students, I'd expect it to look a bit different than the MD student distribution. There are plenty of DO students who want allopathic residencies for a variety of reasons, and/or want specialties that require a good score, and probably prepare well and do well on the USMLE. So I'd expect the curve to be skewed with a greater percentage of DO students failing on the low end, with reasonably similar percentage relative to MD students scoring in the top quartile on the top end. I think the content differences and test taking abilities will probably keep that from being the equal of MD students, but I'm guessing it is much closer than on the lower end.
In any case, a 20-30% of DO students failing an exam whose sole purpose is to certify that the student has the minimal level of proficiency to progress in medical education is alarming and sad. The DO curriculum and/or COMLEX should not be so different as to cause this to be the case. Nor should the academic abilities of the students be so different as to cause this. It could be either, or both, or neither, and I don't know for certain. I can speculate. Hopefully, the trend will continue upwards for many years to come. Only when the pass rates (and averages?) are similar will DO's make further progress to being universally accepted.
