Why do we need fair tests of treatments in health care? Have not doctors, for centuries, “done their best” for their patients? Sadly, there are many examples of doctors and other health professionals harming their patients because treatment decisions were not informed by what we consider now to be reliable evidence about the effects of treatments. With hindsight, health professionals in most if not all spheres of health care have harmed their patients inadvertently, sometimes on a very wide scale. Indeed, patients themselves have sometimes harmed other patients when, on the basis of untested theories and limited personal experiences, they have encouraged the use of treatments that have turned out to be harmful.

The question is not whom we might blame, but whether the harmful effects of inadequately tested treatments can be reduced. They can, to a great extent, firstly, by avoiding applying untested theories about the effects of treatment in practice, and secondly, by wider use of fair tests of treatments. What are fair tests of treatments? They are tests that take steps to obtain reliable information about treatment effects by reducing the misleading influences of biases and the play of chance.

WHY THEORIES ABOUT TREATMENTS MUST BE TESTED IN PRACTICE

Van Helmont 1662

People have often been harmed because treatments have been based on our theories about how disease should be treated without testing the theories in practice. For example, for centuries we believed the theory that illnesses were caused by “humoral imbalances.” So patients were bled and purged, made to vomit and take snuff, in …