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Evidence-Based Dermatology: Research Commentary
March 2001

Challenges to the Hierarchy of Evidence: Does the Emperor Have No Clothes?

Author Affiliations

DamianoAbeniMD, MPHMichaelBigbyMDPaoloPasquiniMD, MPHMoysesSzkloMD, MPH, DrPHHywelWilliamsPhD, FRCP

Arch Dermatol. 2001;137(3):345-346. doi:10-1001/pubs.Arch Dermatol.-ISSN-0003-987x-137-3-drc00008

A Comparison of Observational Studies and Randomized, Controlled Trials

Benson K and Hartz AJ

N Engl J Med. 2000;342:1878-1786

Randomized, Controlled Trials, Observational Studies, and the Hierarchy of Research Design

Concato J, Shah N, and Horwitz RI

N Engl J Med. 2000;342:1887-1892

An important tenet of evidence-based medicine is that there is a hierarchy of evidence. For studies of therapy, in descending order, this hierarchy consists of meta-analyses of randomized clinical trials, randomized controlled clinical trials with narrow confidence intervals, cohort studies, case-control studies, large case series, expert opinion, and in vitro and animal studies. It has been claimed that observational studies find stronger treatment effects than randomized controlled trials. Two recent studies published in the New England Journal of Medicine challenge the veracity of this tenet.1,2

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