Comparative-effectiveness research (CER), which is not a new concept, has succeeded evidence-based medicine as the current fashion. In the old days of evidence-based medicine, active treatment comparators were not banned and one of the major concerns was the choice of outcomes important to and for patients. For instance, high blood pressure itself is an asymptomatic condition, but its devastating clinical complications such as a heart attack or a stroke are not. So, the two movements are similar, one succeeding the other. Perhaps the major difference is the existence of the legislative mandate (PL 111-148), which at once enables and constrains CER.

In a Medline search, I found 44,344 citations for the venerable discipline of evidence-based medicine, 17,140 for the up-and-coming genre of CER, but only 8 for the much-avoided option of opinion-based medicine. No one I know boasts a serious allegiance to opinion-based medicine. This one-sided distribution of published studies strikes epidemiologists like me as odd. Evidence is generally clear; but its validity, interpretation, and generalizability remain a source of active contention. The appeals to evidence, reason, and science are almost universal; but these rhetorical devices may do little to clarify the nature of the process and the disagreements, which often reflect differences in values and assumptions. Indeed, the models of the behavioral economists may provide more insight into this historical process than the rational-choice models of the traditional economists.