Answering USMLE Type Questions – Part I

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To illustrate; a one step thinking question using clinical vignette will look like this

A 40 year old male came back from a recent trip to Mexico 3 days ago. He presents to you with bloody diarrhea, abdominal cramps and fever. You admitted him to the hospital for workup. Sigmoidoscopic examination reveals ulceration in the cecum and ascending colon. Microscopic examination of the biopsy specimen showed flask-shaped mucosal ulcers with extensive necrosis and a modest nonspecific inflammatory response. The ulcers do not penetrate the muscularis propia. The patient admitted to self-medicating with antibiotics. The most likely organism that is responsible for this patients diarrhea is

  1. Giardia Lamblia
  2. Entamoeba histolytica
  3. Shigella
  4. Clostridium difficile
  5. Salmonella

This is actually already a two step thinking, albeit an easy one since one step thinking will ask the diagnosis, like ameobic colitis, pseudomembranous colitis, Giardiasis, Shigellosis or Salmonellosis. Three step thinking will give you choices about specific characteristic of the organisms like

  1. have two stages, trophozoite and cyst and positive string test
  2. have two stages, trophozoite and cyst and cause anchovy paste abscess of the liver
  3. nonlactose fermenting gram negative rods that do not produce H2S
  4. gram positive rods that produce exotoxin A and B.
  5. nonlactose fermenting gram negative rod that produce H2S

Another way is to ask you drug of choice or treatment of choice. Which in this case would be Metronidazole. To make it even harder, the question would say the patient was given the treatment of choice and ask what a common side effect would be or what the patient should avoid taking during treatment, or what pathogenic mechanism underlie the side effect. (Answers are severe nausea, vomiting, etc, then alcohol,  then disulfiram effect that blocks enzyme acetaldehyde dehydrogenase causing accumulation of acetaldehyde from alcohol metabolism)

Are there ways to do better in two to three step thinking question? You bet there are and we will talk about strategies and prep methods that will deal with this later. However, the best weapon is still solid grounding in the medical concepts tested by the USMLE.

The third common problem is the extensive use of distractors in the USMLE. The reason for this is as I said before, the habit most people have of not completely memorizing the concepts but relying on answer choices to help them remember the correct answer. In actual clinical practice with live patient, you are not presented with answer choices but more with fill in the blanks and enumeration. As in “The diagnosis is __________” or “the laboratory test I have to order is 1._____, 2._____, 3._______.” Obviously the USMLE do not want people to just be familiar with the concepts and pass the exam. Therefore the use of two to three step thinking questions and distractors are to ensure that students are forced to memorize rather than just familiarize themselves with the concepts.

One of the more common distractors used often is the “true statement that does not answer the question”. You will be surprise how often they use this type of distractor and how often they worked especially on concepts that the examinee has not solidly learned and still a bit hazy. They usually take their toll on the last few blocks when concentration is less and fatigue more.

Using the above example, the question on what pathogenetic mechanism underlie the side effect of the treatment of choice could have a distractor that goes like this. Antibiotics causes alteration of normal bacterial flora in the bowel with overproduction of bacteria that produces extoxins. The right answer could be stated like this. Antibiotics causes disuliram like effects, with alcohol causing nausea and vomiting on concomitant use. Both statements are true statements but only statement 2 answers the question. For example, one question in NBME on Postmenopausal Hirsutism relies on multiple true statements that does not answer the question. Only one statement answer the question.

Other types of distractors are used less often because they can only be used on specific conditions while the first type of distractor can be used almost anywhere. Other common type of distractors include the following

1.       Common misconceptions – for example most people know that AIDS are not transmitted by kissing so will presume that the HIV virus is not found in saliva, which is false

2.       Recent changes in medical concepts – a favorite is a change in drug of choice for various reasons. They will usually also give the old drug of choice or treatment of choice with the new one.

3.       Close sounding names and or diseases in the choice. Since most people memorize or familiarize themselves with concepts by reading aloud to themselves, they can get confused if they do not pay attention to the actual spelling or master the information i.e. Cushing disease vs. Cushing syndrome.

4.       Disease, drugs or other medical concepts that are similar in a lot of aspects except in some small crucial detail, to make sure you know the crucial detail.

Next time we will discuss the various ways you should prep for this and the strategies you can use when answering this type of questions. There are other characteristics of USMLE type questions you should be aware of, but this three are the major ones and the most common pitfalls for most people.

For those in the prep course who are wondering why I haven’t taught you these, they will actually be taught in the latter part of your prep when you start with q Banks and just before the actual examination. As I said the best way to prepare for the examination is to have a solid knowledge base to rely on. Relying on tips and tricks to pass the exam without a solid knowledge base of medical concepts is risky. Having a solid base and relying on the tips and tricks for those extra points to get higher scores is the best approach. So at this stage, you should be building a solid knowledge base. Plus, I am still in the process of building and making the necessary study tools you need for this part of your prep. Although you can build your own study tools, I would rather you study and let me make the tools, just to be sure it’s done right. High Yield Fast Facts is just one of the tools, more are coming.

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