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Identification of Additional Trials in Prospective Trial Registers for Cochrane Systematic Reviews

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  • Wynanda A van Enst
  • Rob J P M Scholten
  • Lotty Hooft

Abstract

Background: Publication and selective outcome reporting bias are a threat to the validity of systematic reviews. Extensive searching for additional trials in prospective trial registers could reduce this problem. We have evaluated how authors of Cochrane systematic reviews currently make use of trial registers as an additional source for the identification of potentially eligible trials. Methodology/Principal Findings: We included 210 systematic Cochrane reviews of interventions published between 2008 and 2010 of which the protocol was first published in 2008. When prospective trial registers were searched we recorded the names of the register(s), the authors' motive(s) and if they yielded any extra trials. Discussion: Trial registers as an additional source of information are gaining acknowledgement amongst Cochrane reviewers. Nevertheless, searches seem to be inefficient as overlapping databases are frequently consulted, while the WHO ICTRP Search Portal that includes the data from all approved registers worldwide is being underused. Moreover, the emphasis is now on the identification of ongoing trials, although the prospective registers offer a broader potential. Further familiarity of registers and guidance how to search and to report will help to implement this as a common method and utilize the full potential of prospective trial registers for systematic reviews.

Suggested Citation

  • Wynanda A van Enst & Rob J P M Scholten & Lotty Hooft, 2012. "Identification of Additional Trials in Prospective Trial Registers for Cochrane Systematic Reviews," PLOS ONE, Public Library of Science, vol. 7(8), pages 1-5, August.
    • Handle: RePEc:plo:pone00:0042812
    DOI: 10.1371/journal.pone.0042812
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    1. Kerry Dwan & Douglas G Altman & Juan A Arnaiz & Jill Bloom & An-Wen Chan & Eugenia Cronin & Evelyne Decullier & Philippa J Easterbrook & Erik Von Elm & Carrol Gamble & Davina Ghersi & John P A Ioannid, 2008. "Systematic Review of the Empirical Evidence of Study Publication Bias and Outcome Reporting Bias," PLOS ONE, Public Library of Science, vol. 3(8), pages 1-31, August.
    2. Ludovic Trinquart & Adeline Abbé & Philippe Ravaud, 2012. "Impact of Reporting Bias in Network Meta-Analysis of Antidepressant Placebo-Controlled Trials," PLOS ONE, Public Library of Science, vol. 7(4), pages 1-8, April.
    3. J. L. Hutton & Paula R. Williamson, 2000. "Bias in meta‐analysis due to outcome variable selection within studies," Journal of the Royal Statistical Society Series C, Royal Statistical Society, vol. 49(3), pages 359-370.
    4. Roderik F Viergever & Davina Ghersi, 2011. "The Quality of Registration of Clinical Trials," PLOS ONE, Public Library of Science, vol. 6(2), pages 1-8, February.
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