Sunday, July 05, 2015

Why don't we have better medical textbook descriptions of disease?

I have a problem with the way medicine describes diseases. It’s not a new problem - it’s bugged me since about my third year of medical school - 1985 that is. I don’t think things have changed much.

To describe my problem, I’ll invent a disease “Y”.  Y has 3 findings - flat feet, pimples, and bad breath. Each occurs in 1/3 of the people suffering from Y.

What’s the probability that someone has flat feet and pimples given that they have Y?

No, it’s not 1/9.

I never said these were independent findings, and I never said they persist. Y starts with flat feet, then is asymptomatic, then patients develop bad breath and pimples. Yvians never have both flat feet and pimples at the same time. The old multiplication rule only works for independent events.

Ok, so you saw this one coming. Obvious, isn’t it? Well, yes, but most textbooks describe diseases as though they were collections of independent events without correlation or sequence or evolution or treatment effects. They provide long lists of symptoms, some of which rarely or ever coexist, followed by lists of findings, tests and so on. They very rarely, almost never, describe the long term sequelae of common acute conditions. (Often that’s because nobody has researched the “natural history” of the disorder. So the section would have to read “we have no idea” most of the time. That would be a start though.)

At the end of reading a classic textbook disease description you might be able to pass your Board exam, but you really have very little idea what the disease looks like, much less how it’s experienced by the patient. Sure, you learn that stuff after 5-10 years of patient care — but, really, that’s nuts.

Another way to learn this is to experience disease first hand - especially if you’re a 50+ physician. My own (one time) 1-2 day episode of vertigo didn’t match the textbook description of acute labyrinthitis or benign positional vertigo — it had features of both. It also left me with a subtle and persistent degradation of my balance - that doesn’t show up in textbooks either. Every 50+ physician can probably tell a similar story - our textbook descriptions of disease are misleading, incomplete, and frustrating.

I don’t think it was always this way. I have a 1930 edition of William Osler’s ‘The Principles and Practice of Medicine’ on my desk, what that book called “symptoms” was more the course of a disease. I wonder if the 19th century editions were even more case based.

We could fix this, but I never see anyone talking about it. We’d have to first admit we had a problem.

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