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Open Badges Editorial

Efficacy assessed in follow-ups of clinical trials: methodological conundrum

Robert BM Landewé

Author Affiliations

Maastricht University Medical Center, Department of Internal Medicine, Rheumatology, P.O. Box 5800, 6202AZ Maastricht, The Netherlands

Arthritis Research & Therapy 2010, 12:132  doi:10.1186/ar3080

See related research by Rantalaiho et al.,

Published: 30 July 2010


Increasingly, we see papers describing the long-term follow-up results of randomised clinical trials. Sometimes, like the article by Rantalaiho and colleagues in the previous issue of Arthritis Research & Therapy, the follow-up extends to more than 10 years. It is not uncommon that authors of such articles describe their results as a comparison of the original treatment groups in the original randomised clinical trial. Methodologically, such a comparison is fallible for several reasons. In this editorial, two important sources of bias that may jeopardise the results of such follow-up studies are discussed: confounding by indication and confounding by trial completion.