Tips on NBME Shelf Exams

Some thoughts for intrepid and probably antsy first-years as they stumble upon this page on their search for the truth. Here are some tidbits about the Anatomy, Physiology, Biochemistry, and Microbiology shelves.

Anatomy:

Anatomy, if learned well over the year, is doable. It is crammable if (and only if) you’ve actually paid attention and learned everything once. This is not the time to learn anything for the first time. Even with a good background, it tests a ton of material. Pay special attention to high yield parts—things that are often injured or easily framed in a clinical vignette. While everything is there, it’s not there equally often.

For example, collateral circulation is a big favorite for several systems. You’ll see questions that involve artery transection from stab wounds as well as a occluded arteries from cholesterol plaques. You need to know what other arteries can supply these areas–they’ll be there in spades. Focus not just on knowing body parts but also on 3d relationships between body parts, because they’ll often ask for one part in relation to another (the structure immediately lateral to the X is….).

Lastly, pay attention to common injuries and conditions. If someone falls on an outstretched hand, what bone is probably broken? Scaphoid. What bone is most likely dislocated? Lunate. So on and so forth.

Physiology:

Memorize lab values, especially if you’re the type who doesn’t finish tests quickly (this is also a time-saver on the Step 1). More so than other shelves, Physiology clinical vignettes often include lab values that are actually key to understanding what’s wrong (not the case for Microbiology, for example, where lab values are almost always superfluous). Because the test demands more problem solving/reasoning over rote memorization, the physio test is also one of the more tiring, in my humble opinion.

Almost all physio questions require knowledge of the various trends and formulas; they usually demand that you know why something happened or what happens next. For example, you need to know the body’s compensatory mechanisms to keep fluid volume stable, and how these are used to correct for hemorrhage, dehydration, diabetes insipidus, etc etc etc.

Also, know your renal.

Biochemistry:

Buy a set of notecards and memorize them. Know all of the incredibly rare diseases and what enzyme is deficient in the pathway. Not much to say here: it’s a hard test. The things that are most often covered in detail in your biochemistry class are the things you must know in greater detail. So, you have to know metabolism incredibly well. Intimate knowledge of pathways like glycolysis, glycogenolysis, and gluconeogenesis is very high yield. For less important topics, like microtubules, basic gist-level knowledge is sufficient.

Microbiology:

The most crammable exam. First, know basic virology and bacteriology. How they work, change, evolve etc. You definitely must learn about the multiple ways bacteria become virulent and gain new genetic material. A lot of the test comes directly from the sort of stuff everyone overlooks when they start memorizing pathogens.

Second, for clinical vignettes, a good notecard set is always helpful. For most pathogens, there are a handful of key words that will set you off to the question—they usually ask for either an identification or a secondary fact about it. Everything else in the question is just time-wasting fluff. Memorize the key relationship, and you will be fine on the majority of the vignettes. Will you really understand what’s going on? Probably not, but these questions are often designed to test your knowledge of these stereotypical cases, not whether or not you’ll actually be a competent physician.

For example, H. pylori, which causes gastric ulcers produces urease. If you see a patient with an ulcer, the answer is probably either the ID or the enzyme. Aspergillus makes a “fungus ball.” Coccioides is a spherule in the body. People who get a non-healing lesion after being pricked by a rose thorn have an infection from Sporothrix. If a bacteria is coagulase positive, it’s Staph aureus. It really is that superficial. Key word > answer. The difficulty comes from information overload. The more rare the disease, the more likely the question will be an easy form of memory recall (e.g. fever that goes up and down (undulates) is Brucellosis). For more common bugs like Staph and Strep and the very well known diseases (Malaria, TB, etc)—do a better job nailing down greater details.

And that’s it. You’ll be fine.

NBME Shelf Exam scores, with a grain of salt

The NBME Shelf exams are enjoyable standardized tests that every first year looks forward to with almost unbearable glee. They test a single subject (“Anatomy”) and apparently take the relevant questions from the USMLE Step 1, a test that makes the MCAT look like the GRE and the SAT look like building with Lincoln logs.

Some schools force their students to take a variety of Shelf exams (spending/wasting $30 a pop) to help measure how well their students have mastered the material (AKA how they are doing compared to their national counterparts). What is a bit amusing and misleading about the whole ordeal is that the national norms are probably a big crock.

Different schools use the “shelves” differently. Some use them as a just-for-fun intellectual exercise, others as extra-credit, and still others as a true final exam. Don’t get me wrong, it’s not a bad thing to get some USMLE Step 1 experience, but it’s highly dependent on the environment: if you take five step exams in a single week, you are clearly not going to be prepared or even particularly focused. If it’s your final exam, you are going to do your best to rock it.

So if the national average is computed from all of these groups together, then it’s going to have a huge unseen left tail: if people are taking the exam who don’t care how they perform, they’re going to be dragging the average down from where it would otherwise be. So while the test is technically normalized, it’s not the same normal as a regular standardized test: Unlike the MCAT, not every student has something riding on the exam. I personally knew people who filled out all C’s on an exam that was for extra-credit only.

While your school receives the group’s average and your grade relative to your test group (classmates), the theoretically more interesting numbers a student receives are the grade based on the national average and corresponding percentile. I’m curious as to how far off the scores really are. If all those people who weren’t making a good faith effort actually tried (as they do on the USMLE Steps 1, 2, 3), then I’d wager it’d be a different ball game. It’s essentially an unstandardized standardized test.

PTSD: DIY treatment

ABC News ran a story last month about the secret lives of 7-well known drugs. They mention, among other the things, the off-label uses of Viagra. There is a study, apparently, looking into using Viagra as a treatment for jet lag. I hope they administer it with some extra tight underwear: its got quite the side effect.

And then they mention the use of the otherwise illegal party drug Ecstasy to treat post-traumatic stress disorder, or PTSD. But while ecstasy is still very much illegal, there is another widely-available drug that might do the trick, without making you want to hump the street lamp outside the club: Propranolol, a beta-blocker used to treat hypertension.

Propranolol purportedly attenuates memory consolidation by taking the amygdala, our brain’s almond-shaped fear center, offline. Many neuroscientists think of PTSD as a faulty memory loop, where “re-living” a traumatic memory simultaneously reinforces it, over and over again. The emotional valence of these memories is what gives them their terrible power—propranolol is thought to block this emotionally-driven reconsolidation, making these painful memories into more mundane ones: think about what you remember from 9/12/2001 versus 9/11.

The literature has shown conflicting results. Some studies have shown no “significant” benefit for prophylactic use of propranolol after a potentially-traumatic, nor has simple administration of the medicine appeared to reduce PTSD significantly. From the original experiments, these findings aren’t surprising: it’s a pretty mild drug and its effects on memory are not robust (it is likely, however, a harbinger of drugs to come). Still, results have been promising enough to warrant a bevy of studies to examine its effects.

So, if one were to try to re-create a scenario where propranolol would do the trick (which one should never ever do unless involved in a study, of course), the key would be to actively think about the painful memories while taking the drug to dampen your emotional arousal. For war veterans, one would imagine them watching footage from battle, reading scripts that evoke specific scenarios—the very things that would normally trigger the exact thing we want to avoid. The basic idea is to experience the memory without the panic attack (thanks to the medication), and to do this repeatedly until our brains no longer associate the memories with the emotions. The same logic could be applied to overcome phobias in conjunction with cognitive behavior therapy (people already use/abuse beta-blockers off-label to treat social-anxiety symptoms anyway)—you never know, until someone gets federal funding to try.

Lip service surveys

The world is full of surveys: surveys for free meals at TGI Friday’s, surveys for news polls, and at school, surveys for curricular reform:

“In order to improve this course for next year, we would appreciate it very much if you would take a few minutes and fill out this evaluation form.”

And the idea behind a survey is a good (nay, excellent) one: to gather feedback and ostensibly make changes and corrections based on it. The issue is in survey construction and follow-through. The usual survey has a variety of broadly worded statements with answer choices 1-5, 1 being “strongly agree” and 5 being “strongly disagree.” There will usually be a text-box for general comments at the end. You take this survey and your answers disappear into the depths of the internet never to be heard from again.

But from the beginning, the idea that you can sum up whether something works effectively or not based on a numerical average is a kludge. Furthermore, even if an average of 4 does approximate satisfaction, that doesn’t mean there aren’t better ways to do things. It’s an understandable shorthand, but anyone hoping that it’s sufficient to understand reception  is fooling themselves. If people’s responses show that weekly quizzes are on the whole useful, that doesn’t mean they wouldn’t prefer or think it better if they were biweekly, on Mondays, on Fridays, longer, shorter, or anything else. If people say dividing the year into 4 chunks is no good, it doesn’t mean 7 would be better. A number is all well and good, but at the end of the day, how someone feels isn’t the crux: it’s why they feel the way they do.

In order for a survey to be effective, it has to take time. Each question needs to have its own comment box. Then, someone needs to go through those comment boxes and compile all of the suggestions and problems. Take the suggestions and complaints, then formulate new courses of action. Then, before implementing them, offer them anew in a survey:  What do you think about these choices? Do they sound good? How good? Better then before? If not, why not? If that takes too much time to do, have students volunteer to do the grunt work. They’ll put in on their CVs, the administrators can continue doing whatever it is that administrators do, and everyone is happy. This is also how you make changes quickly. It doesn’t need to take years.

People tend to make incremental changes to the status quo. It’s hard to make drastic changes, especially if those changes reverse your hard work or go against your own inclinations; it’s even harder to come up with these changes yourself when necessary. This difficulty then breeds the stagnation that allows bad systems to continue even when their obsolescence is practically taken for granted. And yet, this is how you get curricular form with a stethoscope on the heartbeat of a student body.

Sometimes things don’t work—but if a goal is truly to teach a subject effectively, then no one can tell you better what does and does not work than students. This is how you don’t spin your wheels around a problem, making arbitrary changes. You need to ask for feedback, but more importantly, you need to be willing to listen to it.

Anatomy of an NBME Shelf Exam

The NBME offers comprehensive subject exams, ostensibly to torture students and devour whatever scraps of self-worth they have left. The typical question format:
A X-year-old [type of person] reports to the doctor/ER with a X-hour/day/week/month/year history of not-feeling-so-hot. Upon examination, distracting details. Irrelevant information. Single key relationship. More words to make the test take longer. Talkie-talkie. What is the likely cause of this you-should-have-learned-in-your-class-and-probably-did-but-maybe-you-didn’t-who-knows-there-are-so-many-questions-on-this-test-it’s-all-a-blur person’s problem?
Rinse and repeat for three hours. Then do it for it every class you take. The joys of biochemistry could never be fully appreciated until they were compiled in such a form.