Tuesday, February 09, 2016

Medical knowledge diffusion: The osteoarthritis example

For personal reasons I’ve been doing a deep dive into current medical knowledge of osteoarthritis — particularly the relatively early and aggressive diffuse joint condition i’m enjoying.

It’s given me an opportunity to compare what’s in a current Internal Medicine textbook (Harrison’s 18th edition, 2012) vs. a current Rheumatology text (Hochberg, 6th ed, 2015) vs. the medical literature. 

There’s a relatively clear trend. Harrison’s has vestiges of the 1980s and 1990s view of OA, which focused on injury and “wear and tear” and treats OA as thought it is a single disorder. It is cautious about exercise and joint use. There’s no way to slow, much less reverse, disease progression.

Hochberg, the specialist text, deprecates “wear and tear” and focuses on genetics, but inflammation is mostly a secondary response to some relatively unspecified joint process. In this text OA is a “heterogenous disorder”, which is a pedantic way of saying it’s a whole bunch of things that need to be divided up better. Hochberg is keener on exercise. There’s still no way to slow, much less reverse, disease progression.

The literature, of course, is all over the place, but there’s a consensus for dividing OA up into more useful diagnostic categories. In general exercise is encouraged with little caution. There’s a movement to treat some kinds of OA as a primary disorder of the pre-vertebrate ancient innate immune system (vertebrates also have an adaptive immune system). There are experiments now with medications which act on the innate immune system, like H3 blockers. Of course to be effective these would need to start early in what feels to some like a fast moving disease.

Future versions of Hochberg may or may not incorporate the medical literature. Some quite nice studies have sown that the medical research literature is usually misleading or flat out wrong; most physicians are wise to avoid it. I am, however, a bit disappointed that Harrison’s seems to lag behind Hochberg — the authors are drawn from a similar pool of researchers. Maybe it’s simply that Harrison’s 19th edition is due out shortly, the one I read was probably written five years ago.

For a family physician, internist or geriatrician one lesson might be to stop reading the “generalist” textbooks and skip to the specialist textbooks. Harrison’s is famously unreadable, Hochberg is actually an easier slog. This assumes one has online access to both of course, these are very expensive references.

See also

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