controlled trial

The controlled trial - A scientific method of testing the effectiveness of new treatments or of comparing different treatments.

In a typical controlled drug trial, two comparable groups of patients with the same illness are given courses of apparently identical treatment. Only one group, however, actually receives the new treatment; the second group (known as the control group) is given a placebo (a harmless substance containing no active ingredients). Alternatively, the control group may be given an established drug that is already known to be effective. After a predetermined period, the two groups are assessed medically. If the patients on the new treatment show a greater improvement than those on the placebo (or those on an existing treatment), this result proves that the drug has a beneficial effect.

Controlled trials must be conducted “blind’’ (meaning that the patients do not know which treatment they are receiving). In a “double-blind’’ trial, neither the patients nor the doctors who assess them know who is receiving which treatment.