, Volume 18, Issue 4, p 399
Date: 25 Feb 2009

Do not test for baseline imbalances unless they are known to be present?

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Editor

Fayers and King [1] are correct to “not suggest that one should never carry out significance tests on baseline characteristics” but they also state that “significance tests are pointless in a conventional (individual patient) randomized trial that has an effective randomization procedure [and] are usually [worth doing only] if potential violation of the randomization is suspected.” This advice is analogous to drivers wearing a seatbelt only when they expect to be in an accident. The flaw in the argument is the circularity in suggesting that one can know the results of an analysis without actually conducting this analysis. That is, “the basis for suspicion of flawed randomization can be the very tests of baseline balance that would not be performed, under this approach, without prior suspicion” [2, p. 125]. Moreover, it is not true that in individually randomized trials:

“at the time the patient enters into the trial neither the patient nor the clinical team know which treatment wi ...