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Friday, February 26, 2010

How Doctors Think

@nybooks I've been looking at the work of Jerome Groopman, author of How Doctors Think, as well as a number of recent articles in the New York Review of Books.

Errors of judgement

Groopman discusses the seminal work of psychologists Amos Tversky and Daniel Kahneman, who challenged the prevailing notion that the economic decisions we make are rational. (This field of study is  known as behavioural economics.) We are, they wrote, prone to incorrectly weigh initial numbers, draw conclusions from single cases rather than a wide range of data, and integrate irrelevant information into our analysis. Such biases can lead us astray.

It seems doctors are not immune to such cognitive errors.
Some 10 to 15 percent of all patients either suffer from a delay in making the correct diagnosis or die before the correct diagnosis is made. Misdiagnosis, it turns out, is rarely related to the doctor being misled by technical errors, like a laboratory worker mixing up a blood sample and reporting a result on the wrong patient; rather, the failure to diagnose reflects the unsuspected errors made while trying to understand a patient's condition.

Groopman quotes an associate, a senior cardiologist, who made fatal errors by relying too heavily on logic.
"Impeccable logic doesn't always suffice. My mistake was that I reasoned from first principles when there was no prior experience. I turned out to be wrong because there are variables that you can't factor in until you actually do it. And you make the wrong recommendation, and the patient doesn't survive. I didn't leave enough room for what seems [sic] like minor effects."


Best Practice

As a way of improving diagnosis, there is growing reliance on "clinical guidelines", the algorithms crafted by expert committees that are intended to implement uniform "best practices".

Behavioural economics provides a justification for the proliferation and dissemination of "best practices" to healthcare professionals. If doctors are prone to systematic errors, then best practices will protect them and their patients from the consequences of these errors. Medical best practices are encouraged from President Obama downwards.

But there are some big problems with this approach, as Groopman explains.

Over the past decade, federal "choice architects"—i.e., doctors and other experts acting for the government and making use of research on comparative effectiveness—have repeatedly identified "best practices," only to have them shown to be ineffective or even deleterious.


What may account for the repeated failures of expert panels to identify and validate "best practices"? In large part, the panels made a conceptual error. They did not distinguish between medical practices that can be standardized and not significantly altered by the condition of the individual patient, and those that must be adapted to a particular person. For instance, inserting an intravenous catheter into a blood vessel involves essentially the same set of procedures for everyone in order to assure that the catheter does not cause infection. Here is an example of how studies of comparative effectiveness can readily prove the value of an approach by which "one size fits all." Moreover, there is no violation of autonomy in adopting "aggressive" measures of this kind to assure patient safety.

But once we depart from such mechanical procedures and impose a single "best practice" on a complex malady, our treatment is too often inadequate. Ironically, the failure of experts to recognize when they overreach can be explained by insights from behavioral economics.

Next Practice Tools

How Doctors Think has an epilogue with advice for patients. Groopman gives the following tools that patients can use to help reduce or rectify cognitive errors:
  • Ask What else could it be?, combating satisfaction of search bias and leading the doctor to consider a broader range of possibilities.
  • Ask Is there anything that doesn't fit?, combatting confirmation bias and again leading the doctor to think broadly.
  • Ask Is it possible I have more than one problem?, because multiple simultaneous disorders do exist and frequently cause confusing symptoms.
  • Tell what you are most worried about, opening discussion and leading either to reassurance (if the worry is unlikely) or careful analysis (if the worry is plausible).
  • Retell the story from the beginning. Details that were omitted in the initial telling may be recalled, or different wording or the different context may make clues more salient. (This is most appropriate when the condition has not responded to treatment or there is other reason to believe that a misdiagnosis is possible.)
[source: Wikipedia]


Plenty of good advice there, not just for healthcare professionals but for anyone dealing with complex system problems.

1 comment:

  1. There is much more to this than meets the eye. There was a consumer programme on Radio4 the other day asking whether alternative treatments should be better regulated. The best estimates of misdiagnosis rates in the NHS are upwards on 10% on no data and the best estimates of people killed by the NHS are 25,000 per year. And they want to regulate the only people outside the sytem. We are not even within sight of a situation where patients or doctors can address the evidence, because the worldview of the people who could provide evidence is completely skewed by the industry.

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