Thursday, August 30, 2007

Mechanical or Intuitive Medicine?

Megan McArdle links to this Charles Lambdin review of the book, How Doctors Think, by Jerome Groopman. Now, I have not read Groopman's book, and it is intellectually irresponsible to comment on books you haven't read, but what the heck -- I'm just a D-List blogger, after all.

Lambdin's main criticism of Groopman's book is focused on Groopman's hostility toward "evidence-based medicine." Silly me, I thought all medical science was supposed to be evidence-based -- I thought that was what distinguished Western Medicine from accupuncture and homeopathy and the rest of the woo-woo stuff. But apparently not, and, at least if you believe Lamdbin, Groopman is on the side of the woo-woos. Groopman apparently admits that doctors, like all of us, have a whole array of cognitive biases, that they are inconsistent over time, and that such inconsistency affects their diagnostic accuracy. Yet, despite that, Groopman objects to attempts to make medical diagnoses more accurate through the use of statistical aids:

Groopman tells us he is troubled that new doctors seem to be trained to “think like computers,” that they rely on diagnostic decision aids and some seductive “boiler-plate scheme” called evidence-based medicine. Groopman’s position, when his various arguments are gathered and assembled, becomes untenable. He admits doctors suffer from innumerable biases that diminish the accuracy of diagnosis, reducing many diagnoses to idiosyncratic responses fueled by mood, whether the patient is liked or disliked, advertisements recently seen, etc. Thus Groopman agrees with decision scientists’ diagnosis of doctor decision making; but then he goes on to wantonly dismiss what many of the very same researchers claim is the best (and perhaps only) remedy, the way to “debias” diagnosis: evidence-based medicine and the use of decision aids. In place of statistics what does Groopman suggest doctors rely on? Clinical intuition of course, the very source of the cognitive biases he pays lip service to throughout his book.

Groopman, though, is not alone. Many doctors don't like "mechanical" evidence-based approaches:

Most doctors do not like decision aids. They rob them of much of their power and prestige. Why go through medical school and accrue a six-figure debt if you’re simply going to use a computer to make diagnoses? One study famously showed that a successful predictive instrument for acute ischemic heart disease (which reduced the false positive rate from 71% to 0) was, after its use in randomized trials, all but discarded by doctors (only 2.8% of the sample continued to use it). It is no secret many doctors despise evidence-based medicine. It is impersonal “cookbook medicine.” It is “dehumanizing,” treating people like statistics.

The reason why "treating people like statistics" is better is that it works.

I've been to Vegas a time or two, and somehow I end up seated at a blackjack table. When I find myself in such a situation, I play something called "basic strategy" -- a set of mechanical rules for how to play based upon my cards and the dealer's cards. Now, I wish I could say that basic strategy results in my beating the house, but the truth is that all it does is reduce the house edge to about 1% and means I lose my money at a relatively slow rate.

Sometimes I've been seated next to somebody utterly convinced his or her intuitions or hunches are better than playing the odds. Sometimes they really do get a five when the they hit sixteen and the dealer has a six up. You can be sure they notice every instance in which a deviation from basic strategy pays off. But they don't notice all the times their "hunches" cause them to get hammered. Apply the same woo-woo approach in medicine, and you get crap like this, bleating on about the wonders of intuition. Playing the odds still works better. That's why they are the odds.

As Megan observes, it's natural to resist the idea of using a formula, even when the formula works:

Every profession resists being told that there is a standard way to do things, that a cookie cutter can cut better than their skilled hand. Journalists famously hate the "inverted U" style of writing a news story, even though it really does seem to work better than anything else; it's boring to write, and leaves no room for individual style. Teachers don't like "teaching to the test" or rigidly programmed phonics curricula, even though the latter produces measurably better results than all but the very best teachers. Unfortunately, for many of us, it may be time to welcome our new robot overlords.

All Hail the Robot Overlords!

The point that neither Megan nor Lambdin makes, however, is that this ties in with health care regulations. It's quite possible that a system of mechanically-trained nurse practitioners armed with expert systems and a few doctors in the loop to handle genuinely difficult problems would work better than the current system of state-licensed High Priests. But the current system of compulsory licensure laws prevents any such competing model from emerging.

I do grant that there is some consumer-protective component, that quacks and weirdos and undoubtedly-sincere homeopaths and natural-food junkies are, to some degree, deterred by current compulsory licensure laws. But it also creates barriers to entry for anybody proposing a radically new model, even if such a model might work better.