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Open Access Highly Accessed Open Badges Commentary

Five questions that need answering when considering the design of clinical trials

Timothy Clark1, Hugh Davies2* and Ulrich Mansmann1

Author Affiliations

1 Institut für Medizinische Informationsverarbeitung, Biometrie und Epidemiologie (IBE), Faculty of Medicine, Ludwig-Maximilians University, Munich, Germany

2 Health Research Authority, Skipton House, London SE1 6LH, UK

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Trials 2014, 15:286  doi:10.1186/1745-6215-15-286

Published: 16 July 2014


Evidence suggests that research protocols often lack important information on study design, which hinders external review. The study protocol should provide an adequate explanation for why the proposed study methodology is appropriate for the question posed, why the study design is likely to answer the research question, and why it is the best approach. It is especially important that researchers explain why the treatment difference sought is worthwhile to patients, and they should reference consultations with the public and patient groups and existing literature. Moreover, the study design should be underpinned by a systematic review of the existing evidence, which should be included in the research protocol. The Health Research Authority in collaboration with partners has published guidance entitled ‘Specific questions that need answering when considering the design of clinical trials’. The guidance will help those designing research and those reviewing it to address key issues.

Research protocol; Research question; Ethical research; Systematic review; Sample size; Design assumptions; Justification; Monitoring; Study registration; Publication