Arnold Kling  

Probability and Medicine

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Richard Friedman writes,


The truth is that random events can make or break us. It is more comforting to believe in the power of hard work and merit than to think that probability reigns not only in the casino but in daily life.

I think that a lot of perceptions about health care policy are based on a binary model in which if you receive treatment you are cured, and otherwise you are not. The probabilistic model is more subtle but more accurate.

For Discussion. For a typical patient, should the doctor quote probabilities, or simply tell the patient what to do?


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COMMENTS (8 to date)
Randy writes:

I can only speak for myself here, but that is one of the reasons I like the medical websites - because they do give probabilities. Doctors don't necessarily even tell me what they suspect. They just send me for a battery of tests and ask me to make another appointment. Not that I blame them. I realize they don't have time to care about my concerns.

Lancelot Finn writes:

My suggestion for solving the health care dilemma is to CREDENTIALIZE PATIENTS.

First, privatize high school health classes. Let insurance companies and doctors and what-not set up private firms that go around to high schools and teach intensive, high-quality health classes.

Then commission a number of national health-knowledge exams, a bit like the SAT in that everyone takes them, but dealing with knowledge rather than aptitude. At the same time, the government would set up a huge Web Doctor, an AI simulation of a doctor, available free over the internet (paid for with tax dollars, alas, though perhaps advertisements could defray some of the cost). The health-knowledge exam would measure people's ability, using their knowledge of health and of the Web Doctor service, to self-medicate.

The tests would measure the performance of the health-class providers and provide a way of disciplining and motivating them. But the main use would be for the examinees. You bring insurance companies into the deal by getting them to charge lower premiums for those who do well on the test. Provided that the health classes, the Web Doctor, and the test were effective, this shouldn't take much pushing, since health-insurance companies would have an incentive to attract smart, self-medicating customers anyway.

Once all this apparatus is set up, you have given people the means and the incentive to increase their knowledge of health and their ability to self-medicate. Eventually, you can expand the opportunities of patients to get credentialed; they can take more tests and achieve various levels of credentialed-ness; highly credentialed patients could prescribe medicines to themselves, and maybe even defray the costs of their (already reduced) premiums by writing (well-informed) reviews of doctors that they do business with.

Right now, patients might just be confused by probabilities. But increase patients' knowledge, and they'll demand to be given probabilities, and make their own choices.

I think the onus is on the doctor to explain what the odds are. However (and this is difficult given the time pressures caused by the "business" aspects of healthcare) the doc should know that there's a good chance of misunderstanding and provide an example or analogy. It's like what happens in class when you use a term or make a statement that you KNOW will be misinterpreted - we all have illustrations & analogies to help make the point clearer.

Of course, this cuts into the number of patients the doc can see in a given day, so it's probably not going to happen.

mark writes:

I am an oncologist. I frequently quote probabilities when discussing treatment options with my patients.
Do the ever increasing numbers of casinos show that people do not understand probability?

jaimito writes:

To Mark, of course people does not understand probability. They misunderstand it not only by gaming in a casino, but in buying insurance against tsunamis, and fearing air travel. Maybe your patients are well versed in probability, like many (not all) economists. You could graph their chances, say 50% to survive 1 year, 20% 2 years, 1% 3 years. The question what they understand.

Dan Boyd writes:

Doctors should quote probablities, if that serves a purpose, but I don't think a doctors should tell anyone what do to, expect in extreme cases of self-inflicting diseases.

Besides everyone is different, some are dumb and some are smart, most somewhere between. They need to relate to patients individually, and in order to do that they need to talk to talk with them, not to them. Some might actually find probabilites helpful, others might not understand, misunderstand or just get scared.

Many doctors could be better at informing the patients of their options, and guide the them to a good decision, rather than telling them what to do.

David Thomson writes:

Credentials are mandatory in a modern day society. I most certainly would feel uncomfortable with an alleged heart surgeon who merely read a few books on the subject. The only real question is which organizations have the right to determine one’s expertise in a particular profession. How might we expand the list?

We outsiders need to rely on established experts. Someone like me simply does not have the time nor the expertise to figure out who knows what they are talking about regarding medical matters. Yes, I can follow the example of Andy Grove of Intel---but this still leaves something to be desired. There are only so many hours in a day.

Randy writes:

Just a thought...

The probability of death is 100%. With that in mind, it strikes me as absurd to spend my children's inheritance in an attempt to live an extra year of two. Yes I need to know probabilities - and costs.

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