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Comment & Response
June 6, 2017

Adjustment Strategies in Studies of Therapy

Author Affiliations
  • 1Department of Epidemiology and Biostatistics, University of Western Ontario, London, Ontario, Canada
JAMA. 2017;317(21):2238-2239. doi:10.1001/jama.2017.4880

To the Editor In a Users’ Guides to the Medical Literature article, Dr Agoritsas and colleagues provided an overview of several methods of adjusting for confounding in studies addressing therapy.1 However, the article contained several statements that I believe are not entirely accurate.

First, the authors stated that “large randomized trials ensure that treatment and control groups are balanced with respect to factors associated with outcomes,” but in fact this balance can be truly ensured only in a trial with an infinite number of participants. Obviously, trials of this size are impossible to conduct in real life.