Evidence-based medicine lacks solid supporting evidence

Tom Siegfried writes: For millennia, medicine was more art than science.

From at least the time of Hippocrates in ancient Greece, physicians were taught to use their intuition, based on their experience.

“For it is by the same symptoms in all cases that you will know the diseases,” he wrote. “He who would make accurate forecasts as to those who will recover, and those who will die … must understand all the symptoms thoroughly.”

In other words, doctors drew general conclusions from experience to forecast the course of disease in particular patients.

But Hippocratic medicine also incorporated “scientific” theory — the idea that four “humors” (blood, black bile, yellow bile and phlegm) controlled the body’s health. Excess or deficiency of any of the humors made you sick, so treating patients consisted of trying to put the humors back in balance. Bloodletting, used for centuries to treat everything from fevers to seizures, serves as an example of theory-based medicine in action.

Nowadays medical practice is supposedly (more) scientific. But actually, medical theory seems to have taken a backseat to the lessons-from-experience approach. Today’s catch phrase is “evidence-based medicine,” and that “evidence” typically takes the form of results from clinical trials, in which potential treatments are tested on large groups of people. It’s basically just a more systematic approach to Hippocrates’ advice that doctors base diagnosis, treatments and prognosis on experience with previous patients. But instead of doctors applying their own personal clinical experience, they rely on generalizing the results of large trials to their particular patients.

You should call this approach the “Risk Generalization-Particularization” model of medical prediction, Jonathan Fuller and Luis Flores write in a paper to be published in Studies in History and Philosophy of Biological and Biomedical Sciences. (It’s OK to call it ‘Risk GP’ for short, they say.) “Risk GP” they note, is “the model that many practitioners implicitly rely upon when making evidence-based decisions.”

Risk GP as a model for making medical judgments is the outgrowth of demands for evidence-based medicine, write Fuller, on the medicine faculty at the University of Toronto in Canada, and Flores, a philosopher at King’s College London in England. It “advocates applying the results of population studies over mechanistic reasoning … in diagnosis, prognosis and therapy.” Evidence-based medicine has set a new standard for clinical reasoning, Fuller and Flores declare; it “has become dominant in medical research and education, accepted by leading medical schools and all of the major medical journals.”

So it seems like a good idea to ask whether the “evidence” actually justifies this evidence-based approach. In fact, it doesn’t. [Continue reading…]

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