Comparing treatments

Comparison should be against active treatments rather than placebos

Clinical decisions about management tend to be influenced by a mixture of factors, including the results of clinical trials, the opinions of experts and colleagues, the characteristics of the patients, previous experiences, and plain old habit (good and bad). Where new drugs are concerned, evidence on efficacy from trials is usually good—better than for other clinical interventions. Regulatory agencies have placed high hurdles in the path of drugs, and manufacturers have pursued the questions of efficacy with rigour.

In the United States the Food and Drug Administration, historically, has required evidence from two placebo controlled trials before licensing a new compound, although some recent approvals have been based on a single trial.1 2 Although these regulatory requirements have been criticised, they generally provide us with good evidence that the drug works under specified conditions. It is often less clear how well the drug will work under different conditions and in patients who do not resemble those in the trials. Less attention has been paid to the scientific principles of generalisation than to those that underpin the conduct …