Most people are surprised to learn that rigorous application of formal rules of evidence to evaluate medical research and decide on the best treatments is a recent phenomenon. They might be just as surprised to learn that health policy is not yet subject to the same approach.
So-called “evidence-based medicine” entails a hierarchy of empirical proof that ranks medical studies according to their quality. Physiological research on animals, or of human responses in laboratory settings, rank low on the hierarchy. Observational studies that compare outcomes for patients who receive particular treatments and control subject who do not rank higher, but may still be misleading.
Convincing studies of drugs and surgical procedures usually come only from randomized trials, in which patients receive treatment or don’t according to a process analogous to a coin flip. Well-conducted randomized trials incorporate additional safeguards against bias, including use of placebo medication that allows investigators to blind patients and caregivers to whether patients are, or are not, receiving active treatment.