The Scientific Admissibility of Evidence on the Effectiveness of Preventive Interventions

Abstract

Soon after the Canadian Task Force on the Periodic Health Examination began its deliberations in 1976, the first of many crucial policy decisions was made unanimously by the members. The policy concerned grounds on which recommendations of the task force would be based. One alternative could have been to depend heavily on the opinion of experts (task force members and consultants throughout the world) and to forge a series of consensus positions on the issues to be decided; the second alternative was to base the recommendations on scientific evidence whenever such evidence existed and to invoke such evidence following explicit, predetermined criteria. The task force adopted the latter approach as its governing policy. In retrospect, that decision, innovative at the time, was the most important one the task force made. The strategy followed in the next three years of deliberation, the process of decision making, and the diffusion of recommendations on disease prevention and health protection were driven by the first decision. The report of the Canadian task force gave preeminence to evidence.

Dr Walter Spitzer piloted the Canadian Task Force on the Periodic Health Examination through its perinatal and formative years. He is preeminently qualified to review the evolution of the methodology of the contributions to this book. Construction of a “hierarchy of evidence” was the critical first step in developing a uniform, systematized approach to evaluating preventability across a broad range of harmful conditions. On this foundation, instead of producing recommendations that were simply for or against any preventive intervention, it was possible to derive recommendations of graded strength in either direction. Dr Spitzer’s exposition is the key to understanding the modus operandi of this book’s contributors.