“The result of this trial speaks for itself!”
This often heard phrase contains a troubling assumption: That an experiment can stand entirely on in its own. That it can be interpreted without reference to other trials and other results. In a couple of articles published over the last two weeks, my co-authors and I deliver a one-two punch to this idea.
The first punch is thrown at the US FDA’s use of “assay sensitivity,” a concept defined as a clinical trial’s “ability to distinguish between an effective and an ineffective treatment.” This concept is intuitively appealing, since all it seems to say is that a trial should be well-designed. A well-designed clinical trial should be able to answer its question and distinguish an effective from an ineffective treatment. However, assay sensitivity has been interpreted to mean that placebo controls are “more scientific” than active controls. This is because superiority to placebo seems to guarantee that the experimental agent is effective, whereas superiority or equivalence to an active control does not rule out the possibility that both agents are actually ineffective. This makes placebo-controlled trials more “self-contained,” easier to interpret, and therefore, methodologically superior.
In a piece in Perspectives in Biology and Medicine, Charles Weijer and I dismantle the above argument by showing, first, that all experiments rely on some kinds of “external information”–be it information about an active control’s effects, pre-clinical data, the methodological validity of various procedures, etc. Second, that a placebo can suffer from all of the same woes that might afflict an active control (e.g., the “placebo effect” is not one, consistent effect, but can vary depending upon the type or color of placebo used), so there is no guarantee of assay sensitivity in a placebo-controlled trial.
The views, opinions and positions expressed by these authors and blogs are theirs and do not necessarily represent that of the Bioethics Research Library and Kennedy Institute of Ethics or Georgetown University.