Wednesday, April 4, 2012

How to make safer decisions in medicine

I love when an article I read first thing in the morning gets me to think about itself all through my morning chores and then erupts into a blog post. So it was with this little gem in the statistical publications "Significance." The author suggests making gambling safer by placing realistic odds estimates right on the poker machines in casinos. He even goes through the generation of the odds of winning and losing and how much based on really transparent assumptions. In fact, what he has in effect constructed is a cost-benefit model for the decision to engage in the game of poker on these machines. Seems pretty simple, right? Just a few assumptions about how long the person will play, some objective inputs about the probabilities, and PRESTO, you have a transparent and realistic model of what is probable.

In medicine, there is a discipline known as Medical Decision Making, and what it does is exactly what you see in the "Significance" article: its practitioners construct risk- (and, hence, cost-) benefit models for decisions that we make in medicine. To be sure,these turn out to be rather more complex, since the inputs for them have to come from a large and complete sampling of the clinical literature addressing the risks and the benefits. But that's the meat; the skeleton upon which this meat hangs is a simple decision tree with "if this then that" arguments. In this way these models synthesize everything that we know about a specific course of action and put it together into a number driven by probability.

They usually go something like this. We have a group of women between 40 and 49 years of age with no apparent risk factors for breast cancer. What is the risk-benefit balance for mammography screening in this specific age layer? One way to approach this is to take a hypothetical cohort of 1,000 women who fit this description and put it through a decision tree. The first decision node here is whether to perform a screening or not. What follows are limbs stretching out toward particular outcomes. Obviously, some of these outcomes will be desirable (e.g., saving lives), while some will be undesirable, ranging from worry about false positive results to unnecessary surgery, chemotherapy, radiation, and even death. Because these outcomes are so heterogeneous, we try to convert everything to monetary costs per quality of life (quality because there are outcomes worse than death, as it turns out). But what underlies all of these models is the mathematics derived from clinical studies, not pulled out of thin air. This is the most useful synthesis of the best evidence available.

To be sure, MDM models are rather more complicated than the poker example. They require a little more undivided attention to follow and understand. Furthermore, I personally did not get a whole lot of exposure to them in my training, but perhaps that has changed. Like anything to do with probability, these models tend to be off-putting in a society that has consigned itself to wide-spread innumeracy. And doctors are certainly not immune from misunderstanding probability. Yet without them perceptions rule, and our healthcare becomes a reckless gamble. In our ignorance we collude to build profits that come with medicalizing small deviations from the perceived normality. Sadly, the primary interests that drive these profits are not usually doing so with probabilistic forethought either, but rather on the basis of red hot conviction that they are right.

Doctors and e-patients need to lead a radical transformation in how we handle decisions in healthcare. It is very clear that willful ignorance has not served us well, and we are all too easily led into panic about every pimple. Resilience can only come when we question our assumptions. Alas, our intuitive brain is almost certain to mislead us when faced with complex information; why else would we need explicit odds listed on poker machines? The absurd complexity of information in medicine deserves no less. It's time to start the probability revolution!

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  1. Hi Marya,
    Thanks for this post. Questioning assumptions is what I live for!

  2. That makes two of us! Thanks, Elaine.

  3. Love it! Bring the skeleton of physician intuition out of the closet, please. The cowboy “physician who follows his gut” (which often seems to also fatten his wallet) model relies on some kind of judgmental infallibility associated with medical training -even when that training taught them little about evaluating evidence and making good decisions. Evaluating evidence, assessing risk, making defensible judgments and including the patient in the decision making process should be an essential part of the medical curriculum.
    But as a very smart physician whispered to me once - psst.... at least half of us graduated bottom of the class.

  4. Hello, Radhika, thanks for visiting my blog! I would love to hear more of your perspective on how we can re-engineer the system. After all, it is not just the doctors that got us here.How is your work impacting this change?

  5. Hi Marya,
    Certainly, I would agree with you that it is not just the doctors that got us here. But I would assert that physicians are creating a lot of the inertia that keeps us here. Most people dislike change and if those who dislike change also have undue influence on a system, then change is certainly harder. We see this in the financial sector today.
    Many physicians perpetuate their "invincibility" by saying that those of us who are non-medicos do not understand and are not smart enough to question their judgment. When I question my physicians and even give them research papers, I am not sure that I am not lumped into some mental category of difficult-thinks-she-knows it all-internet-researching-patient, because I don't change, and sometimes even face condescension.
    In my worklife, I am a researcher at a non-profit association representing medical group managers. My views are not necessarily those of my organization but then again, I am told, I am too idealistic. How is my work impacting change? What a good and tough question. It sounds trite but I try to "do the right thing", try to do my work well and try to speak honestly. I am not sure that I am always affecting change, but I try.

  6. Radhika,

    Yes, thank you, that is exactly the point of view I was looking for -- empowered patient/researcher. I agree that the culture of medicine is resistant to change. And yes some docs don't like dissent -- I don't bother to work with them, as I make it clear that decisions will be made not by them, but by me in consultation with them. This is admittedly easier to accomplish given my credentials, though.

    I believe fervently in patient education and empowerment, that is why I wrote the book. Lay public needs to demand less, not more. I truly believe there are a lot of interventions being done to satisfy our national need for "doing something." If you think I am wrong, just think back to the "death panels." At the same time I agree that we need to change the culture of medicine big time.

    Thanks again for your thoughtful reply. Hope to see you here again.