Cluster-randomised controlled trials evaluating complex interventions in general practices are mostly ineffective: A systematic review

Publication date: Available online 31 October 2017
Source:Journal of Clinical Epidemiology
Author(s): Andrea Siebenhofer, Michael A. Paulitsch, Gudrun Pregartner, Andrea Berghold, Klaus Jeitler, Christiane Muth, Jennifer Engler
ObjectiveTo evaluate how frequently complex interventions are shown to be superior to routine care in general practice-based cluster-randomised studies (c-RCTs), and to explore whether potential differences explain results that come out in favour of a complex intervention.Study DesignWe performed an unrestricted search in the Central Register of Controlled Trials, MEDLINE and EMBASE. Included were all c-RCTs that included a patient-relevant primary outcome in a general practice setting with at least one-year follow-up. We extracted effect sizes, p-values, intra-cluster correlation coefficients (ICCs) and 22 quality aspects.ResultsWe identified 29 trials with 99 patient-relevant primary outcomes. After adjustment for multiple testing on a trial level, four outcomes (4%) in four studies (14%) remained statistically significant. Of the eleven studies that reported ICCs, in eight the ICC was equal to or smaller than the assumed ICC. In 16 of the 17 studies with available sample-size calculation, effect sizes were smaller than anticipated.ConclusionsMore than 85% of the c-RCTs failed to demonstrate a beneficial effect on a pre-defined primary endpoint. All but one study were overly optimistic with regard to the expected treatment effect. This highlights the importance of weighing up the potential merit of new treatments and planning prospectively, when designing clinical studies in a general practice setting.



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