Payment systems must take into account the art of medicine

You know that joke about the farmer whose cows are not producing enough milk? A university panel gathers under the leadership of a theoretical physicist. They analyze each aspect of the problem thoroughly and carefully, and after much deliberation produce a report, the first line of which is “First, assume a spherical cow in a vacuum.”

This joke has become short-hand for some of the reductionist thinking in theoretical physics, but it can just as easily personify the field of statistics, upon which we rely so heavily to inform our evidence-based practices.

Here is what I mean. Let us look at four common applications of statistical principles. First, descriptive statistics, usually represented by Table 1 in a paper, in which we are interested in understanding the measures of central tendency such as the mean and median values. I would argue that both measures are somewhat flawed in the real world. As we all learned, a mean is a bona fide measure of central tendency in a normal or Gaussian distribution. And furthermore, in such a distribution 95% confidence intervals are bounded by 2.5x the standard deviation from the mean.

Although this is very convenient, few things about human biology are actually distributed normally, while many cluster to the left or to the right of the center creating a tail on the opposite side. For these skewed distributions a median is the recommended measure to be used, bracketed by the boundaries of the 25% to 75% range of the values, or the interquartile range. But in a skewed distribution it is exactly the tail that is its most telling feature, as described so eloquently and personally by Stephen J. Gould in his “The Median Isn’t the Message” essay. This is especially true when more specific identification of characteristics precipitates the numbers dwindle; e.g., if instead of such general measures as blood pressure among all-comers you want to focus on morning blood pressures in such specific group as African-American males with a history of diabetes and hypercholesterolemia who attend a smoking cessation program, say. And this is important because at the level of the office encounter each patient is a universe of his/her own risk factors and parameters that does not necessarily obey the rules of the herd.

Second, analytic modeling relies on the assumption of normality. To overcome this limitation we transform certain non-normal distributions to their log forms, for example, to normalize them in order to force them to play nicely. Once normalized, we perform the prestidigitation of a regression, reverse-transform the outcome to its anti-log, and, voila, we have God’s own truth! And even though statisticians tend to argue about such techniques, in the real world of research, where evidence cannot wait for perfection, we accept this legerdemain as the best we can do.

The next example I will use is that of pooled analyses, specifically meta-analyses. The intent of meta-analyses is to present the totality of evidence in a single convenient and easily comprehended value. One specific circumstance in which a meta-analysis is considered useful is when different studies are in conflict with one another, as for example, when one study demonstrates that an intervention is effective, while another does not show such effectiveness.

In my humble opinion, it is one thing to pool data when studies suffer from Type II error due to small sample sizes. However, what if the studies simply show opposite results? That is, what if one study indicates a therapeutic advantage of treatment T over placebo P, but another shows the exact opposite? Is it still valid to combine these studies to get at the “true” story? Or is it better to leave them separate and try to understand the potential inherent differences in the study designs, populations, interventions, measurements, etc.? I am not saying that all meta-analyses mislead us, but I do think that in the wrong hands this technique can be dangerous, smoothing out differences that are potentially critical. This is one spherical cow that needs to be milked before it is bought.

The last cow is truly spherical, and that is the one-on-one patient-clinician encounter, wherein the doctor needs to cram the individual patient with his/her binary predispositions into the continuous container of evidence. It is here that all of the other cows are magnified to obscene proportions to create a cumbersome, at times incomprehensible and frequently useless pile of manure. It is one thing for a clinician to ignore evidence willfully; it is entirely another to be a conscientious objector to what is known but not applicable to the individual in the office.

But let’s remember that I, as a health services researcher and a self-acknowledged sustainability zealot, am in awe of manure’s life-giving properties. Extending the metaphor then, this pile of manure can and should be used to fertilize our field of knowledge by viewing each therapeutic encounter systematically as its own experiment. The middle way is that between the cynicism of discarding and blind acceptance of any and all evidence. That is where the art of medicine must come in, and the emerging payment systems must take it into account. Doctors need time, intellectual curiosity and skills to conduct these “n of 1″ trials in their offices. If the fire hose of new data insists on staying on, this is the surest way to direct “conscientious and judicious” application of the resulting oceans of population data in the service of our public’s health. And that should make the farmer happy, even if his cows are spherical.

Marya Zilberberg is founder and CEO of EviMed Research Group and blogs at Healthcare, etc.


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  • paul

    unfortunately, cost control is not compatible with taking into account the art of medicine. the only way to truly allow us to treat every individual patient encounter uniquely requires cost to not be a consideration. this is not sustainable… unless there is a two-tiered system where those paying out of pocket can get tailored, individualized care they can choose to pay for or not, and those relying on taxpayers to foot the bill get population-based algorithm health care. question is, will the government allow a two-tiered system?

    of course, true implementation of population-based care requires us as a society to define acceptable miss rates (of something other than “zero”)… which we probably won’t be capable of doing until we are at the edge of the financial oblivion cliff looking over into the abyss. hopefully that won’t happen in my lifetime but i fear for my children and my children’s children.

  • Chris Johnson

    The shorter version of all this is another joke: “Sure, it works in practice. Big deal — does it work in theory?”

  • IVF-MD

    Critical thinkers would approach the problem this way, beginning with an open-minded approach and recognizing that A. It MIGHT be true that there is such a thing as the “art of medicine” that has a certain value or B: It MIGHT be true that there is no such thing as the “art of medicine”

    So who is best-suited to judge this added value? Is it some committee of bureaucrats who do not know the particular physician nor the particular patient nor even the particular community in which the transaction is taking place 2000 miles away from the bureaucrats’ office? Or is it better if this added value is determined dynamically locally and individually by the actual people involved via the complex workings of the free market?

  • Marc Gorayeb, MD

    Reductionist thinking is the source of insight. It is how we learn general principles, and how we can make sense of the world. But portfolio diversification is how average people actually succeed in the real world, how new principles are discovered. If bureaucrats/technocrats are allowed to throttle our choices at the altar of reductionist thinking, then fewer new treatments will be discovered, fewer treatable subgroups will be identified. The lowest common denominator will be served at the expense of the occasional patients who truly benefit from a particular non-standard treatment.

    Consider the experience with Niseritide for CHF. A couple of bad studies scared physicians away from prescribing it. A couple of better follow-up studies showed that it was safe, but did not identify any particular sub-group of patients who would most benefit from it. Now if you were to allow government bureaucrats to restrict its use because it hasn’t been shown to be clearly superior to diuretics and vasodilators, you might never identify individual patients or subgroups who could be saved by this drug.

    It’s reasonable for third party payers to limit reimbursement to non-experimental treatments, but where a treatment has been found to be safe and effective, individual choice needs to be preserved. Unfortunately the single-payer government predilection is to force the average approach upon all recipients, giving rise to counteracting interest group politics and marketing. This in turn distorts the marketplace, which is exactly what we must avoid in order to maximize the social and scientific benefits of true diversification.

  • gzuckier

    Coming from the scientist side of things (and echoing the thoughts of most such people I know), on an individual basis the idea of diagnosis of an abnormal state by test results in the absence of any baseline test results representing the patient’s healthy, normal state, in the belief that the aggregate baseline values determined in population studies can be used, is pretty questionable.

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