What do I need to know to pass the exam?

by reestheskin on 24/06/2021

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After thirty-five years of teaching medical students dermatology the 2021 GMC’s Medical Licensing Assessment (MLA) content map makes for dispiriting reading. The document states that it sets out the core knowledge expected of those entering UK practice. It doesn’t.

My complaint is not the self-serving wish of the specialist who feels that his subject deserves more attention — I would willingly remove much of what the GMC demand. Nor is it that the document elides basic clinical terminology such as acute and chronic (in dermatology, the term refers to morphology rather than just time). Nor, bizarrely, that it omits mention of those acute dermatoses with a case-fatality rate higher than that of stroke or myocardial infarction: bullous pemphigoid, pemphigus, and Stevens-Johnson syndrome/Toxic Epidermal Necrolysis are curiously absent. No, my frustrations lie with the fact that the approach taken by the GMC, whilst superficially attractive, reveals a lack of insight into, and, knowledge of medicine and expertise in medicine. The whole GMC perspective, based on a lack of domain expertise, is that somehow they can regulate anything. That somehow there is a formula for ‘how to regulate’. This week, medicine; next week, the Civil Aviation Authority. The world is not like that — well it shouldn’t be.

Making a diagnosis can be considered a categorisation task in which you not only need to know about the positive features of the index diagnosis, but also those features of differential diagnoses that are absent in the index case (for Sherlock Holmes aficionados, the latter correspond to the ‘curious incident of the dog in the night’ issue). It is this characteristic that underpins all the traditional ‘compare and contrast’ questions, or the hallowed ‘list the differentials, and then strike them off one-by-one’.

Take melanoma, which the MLA content guide includes. Melanoma diagnosis requires accounting for both positive and negative features. For the negative features, you have to know about the diagnostic features of the common differentials that are not found in melanomas. This entails knowing something about the differentials, and, as the saying goes, if you can’t name them, you can’t see them. A back of the envelope calculation: for every single case of melanoma there are a quarter of a million cases made up of five to ten diagnostic classes that are not melanomas. These include melanocytic nevi, solar lentigines, and seborrhoeic keratoses; these lesions are ubiquitous in any adult. But the MLA fails to mention them. What is a student to make of this? Do they need to learn about them or not? Or are they to be left with the impression that a pigmented lesion that has increased in size and changed colour is most likely a melanomas (answer:false).

Second, the guide essentially provides a list of nouns, with little in the way of modifiers. Students should know about ‘acute rashes’ and ‘chronic rashes‘ — terms I should say that jar on the ear of any domain expert — but which conditions are we talking about, and exactly what about each of these conditions should students know?

In some domains of knowledge it is indeed possible to define an ability or skill succinctly. For instance, in mathematics, you might want students to be able to solve first-order differential equations. The competence is simply stated, and the examiner can choose from an almost infinite number of permutations. If we were to think about this in information theory terms, we would say we can highly compress in a faithful (lossless) way what we want students to know. But medicine is not like this.

Take psoriasis as another example from the MLA. Once we move beyond expecting students to know how to spell the word watch what happens as you try to define all those features of psoriasis you wish them to know about. By the time you have you finished listing what exactly you want a student to know, you have essentially written the textbook chapter. We are unable to match the clever data compression algorithms that generate MP3 formats or photograph compressions. Medical texts do indeed contain lots of annoying details — no E=MC2 for us — but it is these details that constitute domain expertise. But we can all agree, that we can alter the chapter length as an explicit function of what we want students to know.

Once you move to a national syllabus (and for tests of professional competence, I am a fan) you need to replace what you have lost; namely, the far more explicit ‘local’ guides such as ‘read my lecture notes’ or ‘use this book but skip chapters x, y and z’ that students could once rely on. The most interesting question is whether this is now better done at the level of the individual medical school or, as for many non-medical professional qualifications, at the national level.

Finally, many year ago, Michael Power, in his book, The Audit Society: Rituals of Verification demolished the sort of thinking that characterises the whole GMC mindset. As the BMJ once said, there is little in British medicine that the GMC cannot make worse. Pity the poor students.