Skip to main content
Article
Searching for unpublished trials in Cochrane reviews may not be worth the effort
Journal of clinical epidemiology
  • Mieke van Driel, Bond University
  • An De Sutter
  • Jan De Maeseneer
  • Thierry Christiaens
Date of this Version
8-1-2009
Document Type
Journal Article
Publication Details
Interim status: Citation only.

van Driel, M.L., De Sutter, A., De Maeseneer, J. & Christiaens, T. (2009). Searching for unpublished trials in Cochrane reviews may not be worth the effort. Journal of clinical epidemiology, 62(8), 838-844.

Access the Journal's homepage.

2009 HERDC submission. FoR code: 1117

© Copyright Elsevier Inc, 2009
Disciplines
Abstract

Objective
To assess the value of searching for unpublished data by exploring the extent to which Cochrane reviews include unpublished data and by evaluating the quality of unpublished trials.

Study Design and Setting
We screened all 2,462 completed Cochrane reviews published since 2000 in the Cochrane Database of Systematic Reviews Issue 3, 2006. In a random sample (n=61) of 292 reviews, including unpublished trials, we studied all 116 references.

Results
Unpublished trials make up 8.8% of all included trials in our sample. Thirty-eight percent of the “unpublished” trials have in fact been published. Allocation concealment was “unclear” or not adequate in 54.3% and 61.3% reported blinding. In 47.2% reported withdrawal rates were >20%. Trials that were eventually published had larger mean population sizes (P-value, 0.02). Of the reported sponsors, 87.3% were drug companies. Methodological quality and publication bias are mentioned in half of the reviews and explored in a third. Quality ratings did not have consequences for pooling, because 82.8% was included in the forest plots.

Conclusions
A minority of Cochrane reviews include “unpublished trials” and many of these are eventually published. Truly unpublished studies have poor or unclear methodological quality. Therefore, it may be better to invest in regular updating of reviews, rather than in extensive searching for unpublished data.

Citation Information
Mieke van Driel, An De Sutter, Jan De Maeseneer and Thierry Christiaens. "Searching for unpublished trials in Cochrane reviews may not be worth the effort" Journal of clinical epidemiology Vol. 62 Iss. 8 (2009) p. 838 - 844
Available at: http://works.bepress.com/mieke_van_driel/8/