A PROSPECTIVE, RANDOMIZED, PLACEBO-CONTROLLED, DOUBLE-BLIND, CLINICAL TRIAL COMPARING ...

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By Frederick "Yaybob" Ziffel (about the author) Page 2 of 2 page(s)

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Double blind[ed]. This means that neither the two patient groups *nor* the clinicians studying them know who is getting treatment and who is getting placebo. Both patients and clinicians are blinded.

To accomplish this, not only must the control group be given a placebo, but also the clinicians who examine and assess them cannot know who has received a placebo. This requires that someone behind the scenes prepare daily packages of medicine and placebo labeled for specific patients, and hand them over to the experimenters to distribute to patients without knowing themselves if they have passed out medicine or placebo in any particular case. When even the clinicians studying the patients are in the dark (blinded) about who is getting the treatment and who is not, the study is called double blinded.

This is important to keep both patients and clinicians from subconsciously skewing their judgments in favor of or against the treatment by suggesting a false benefit or side effect. That is, you might feel better just from knowing that you are receiving treatment, and worse knowing that you are not. Or you might not want to disappoint your doctor if you knew that you were being treated, and report your status more optimistically than is warranted. Or one might report less severe or no side effects if one knew one was given a placebo. We want to measure *only* the drug's physiological effect, not its psychological effect.

CONCLUSION. If all of this can be accomplished, and if the study is sufficiently powered, that is, if a sufficient number of patients in each group are observed long enough (and this is decided in advance by statisticians), one can say that there was or was not a difference between the two groups due to the treatment with a specified degree of certainty. And that is the purpose of any study.

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