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Extent of publication bias in cohorts of studies approved by research ethics committees and included in trial registries

Date and Location




Friday 20 September 2013 - 10:30 - 12:00
Presenting author and contact person

Presenting author

Christine Schmucker

Contact person

Christine Schmucker
Joerg Meerpohl
Abstract text
Background: The synthesis of published research in systematic reviews is increasingly important in providing evidence to inform clinical and health policy decision making. However, its validity is threatened if publications represent a biased selection of all studies that have been conducted (publication bias). Objectives: To investigate the extent of publication bias we conducted two systematic reviews of methodological research projects that determined publication rates and investigated factors associated with full publication of studies approved by (i) research ethics committees (RECs) or (ii) included in trial registries. Methods: We conducted electronic literature searches without language restriction to February 2012. Data were extracted for methodological research projects that reported the publication rate of studies approved by RECs or studies included in trial registries with a minimum follow-up of 24 months. For both reviews separately, we calculated weighted estimates of publication rates (random effects model). Pooled odds ratios (OR) were used to express associations between study characteristics and journal publication. Results: Fifteen methodological research projects following studies approved by RECs and 11 following studies included in trial registries were identified. After REC approval, the weighted publication rate was 45.0% (95%CI 36.7-53.6) and after inclusion in trial registries it was 49.5% (95%CI 35.8-63.2). REC-approved studies with significant results (compared to those without) were more likely to be published (pooled OR 2.8; 95%CI 2.0-3.9). In the cohort of studies followed after trial registration phase-III trials were more likely to be published than early-phase trials (pooled OR 1.9; 95%CI 1.6-2.3). Conclusions: Many studies approved by RECs or included in trial registries remain unpublished. As non-publication is not a random process, our findings support the notion that the dissemination of research findings is biased.