Extent of non-publication in cohorts of studies approved by research ethics committees or included in trial registries

Christine Schmucker, Lisa K. Schell, Susan Portalupi, Patrick Oeller, Laura Cabrera, Dirk Bassler, Guido Schwarzer, Roberta W. Scherer, Gerd Antes, Erik Von Elm, Joerg J. Meerpohl, Vittorio Bertele, Xavier Bonfill, Marie Charlotte Bouesseau, Isabelle Boutron, Silvano Gallus, Silvio Garattini, Karam Ghassan, Carlo La Vecchia, Britta LangJasper Littmann, Jos Kleijnen, Michael Kulig, Mario Malicki, Ana Marusic, Katharina Felicitas Mueller, Hector Pardo, Matthias Perleth, Philippe Ravaud, Andreas Reis, Daniel Strech, Ludovic Trinquart, Gerard Urrú Tia, Elizabeth Wager, Alexandra Wieland, Robert Wolff.

Research output: Contribution to journalArticle

Abstract

Background: The synthesis of published research in systematic reviews is essential when providing evidence to inform clinical and health policy decisionmaking. However, the validity of systematic reviews is threatened if journal publications represent a biased selection of all studies that have been conducted (dissemination bias). To investigate the extent of dissemination bias we conducted a systematic review that determined the proportion of studies published as peerreviewed journal articles and investigated factors associated with full publication in cohorts of studies (i) approved by research ethics committees (RECs) or (ii) included in trial registries.

Methods and Findings: Four bibliographic databases were searched for methodological research projects (MRPs) without limitations for publication year, language or study location. The searches were supplemented by handsearching the references of included MRPs. We estimated the proportion of studies published using prediction intervals (PI) and a random effects meta-analysis. Pooled odds ratios (OR) were used to express associations between study characteristics and journal publication. Seventeen MRPs (23 publications) evaluated cohorts of studies approved by RECs; the proportion of published studies had a PI between 22% and 72% and the weighted pooled proportion when combining estimates would be 46.2% (95% CI 40.2%-52.4%, I2594.4%). Twenty-two MRPs (22 publications) evaluated cohorts of studies included in trial registries; the PI of the proportion published ranged from 13% to 90% and the weighted pooled proportion would be 54.2% (95% CI 42.0%-65.9%, I2598.9%). REC-approved studies with statistically significant results (compared with those without statistically significant results) were more likely to be published (pooled OR 2.8; 95% CI 2.2-3.5). Phase-III trials were also more likely to be published than phase II trials (pooled OR 2.0; 95% CI 1.6- 2.5). The probability of publication within two years after study completion ranged from 7% to 30%.

Conclusions: A substantial part of the studies approved by RECs or included in trial registries remains unpublished. Due to the large heterogeneity a prediction of the publication probability for a future study is very uncertain. Non-publication of research is not a random process, e.g., it is associated with the direction of study findings. Our findings suggest that the dissemination of research findings is biased.

Original languageEnglish
Article numbere114023
JournalPLoS One
Volume9
Issue number12
DOIs
Publication statusPublished - Dec 23 2014

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

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    Schmucker, C., Schell, L. K., Portalupi, S., Oeller, P., Cabrera, L., Bassler, D., Schwarzer, G., Scherer, R. W., Antes, G., Von Elm, E., Meerpohl, J. J., Bertele, V., Bonfill, X., Bouesseau, M. C., Boutron, I., Gallus, S., Garattini, S., Ghassan, K., La Vecchia, C., ... Wolff., R. (2014). Extent of non-publication in cohorts of studies approved by research ethics committees or included in trial registries. PLoS One, 9(12), [e114023]. https://doi.org/10.1371/journal.pone.0114023