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To the Editor: Dr Guyatt and colleagues¹ suggest a hierarchy of study design to evaluate the strength of evidence for making treatment decisions. In promoting the superiority of single randomized trials over systematic reviews of observational studies, the authors risk making the same mistake that evidence-based medicine professes to avoid—relying on personal experience and disregarding the best available evidence.

Randomized trials are not always the best way to evaluate treatment in a given clinical scenario, and poorly conducted randomized trials may lead to erroneous conclusions and produce contradictory results. Evidence suggests that observational studies and randomized controlled trials (RCTs) can produce similar estimates of the effects of treatment,² and that meta-analyses of observational studies produce results that are similar to meta-analyses of randomized trials.³

Furthermore, current rigid hierarchy promoted by Guyatt et al will necessarily place less value on evidence that does not fit into a specific category.⁴ More precise . . . [Full Text of this Article]

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