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Lessons Learned from Attempts To Establish the Blind in Placebo-Controlled Trials of Zinc for the Common Cold
- University of Tennessee College of Medicine—Chattanooga Unit; Chattanooga, TN 37403 (Desbiens)
“ … anything tasting as bad as zinc and with as much aftertaste as zinc must be good medicine” (1).
Where would the evidentiary basis of medicine be without the randomized, double-blind, placebo-controlled trial? Over the past half-century, this type of trial has evolved from being considered an interesting statistical approach to being recognized as the study design associated with the least threat to the validity of findings (2). If only this trial could be applied to the study of every test, treatment, and diagnostic approach in clinical practice! However, with increased application has come greater awareness of its limitations and more critical evaluation of its theoretical underpinnings (3, 4).
In most drug studies that use the randomized, double-blind, placebo-controlled trial, the methods section indicates that patients were randomly assigned to receive the active drug or an “identical placebo.” The empirical basis for this statement is rarely mentioned; ideally, researchers should have demonstrated that patients could not differentiate between the placebo and the study drug. However, in most drug studies, clinical researchers obtain the placebo from drug companies and usually take it on faith that it is “identical” and that the blind has therefore been established.
To prove that the blind has been established in a study, researchers have begun asking patients to guess whether they are taking placebo or active drug. By 1984, 5% of articles in major journals used this enhanced study design (5). Surprisingly, rigorous study of the best way to request the guess has not been done. Possible …
This 100-word excerpt has been provided in the absence of an abstract.
