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Grey matters; on the importance of publication bias in systematic reviews
  1. Marinus Winters1,
  2. Adam Weir2,3
  1. 1Department of Rehabilitation, Nursing Science & Sports, University Medical Centre Utrecht, Utrecht, The Netherlands
  2. 2Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar
  3. 3Amsterdam Centre for Evidence Based Sports Medicine (ACES), Academic Medical Centre Amsterdam, Amsterdam, The Netherlands
  1. Correspondence to Dr Marinus Winters, Department of Rehabilitation, Nursing Science & Sports, University Medical Centre Utrecht, P.O. Box 85500, Utrecht 3508 GA, The Netherlands; marinuswinters{at}

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‘How can I treat my patient best?’ is a question clinicians ask themselves on a daily basis. For clinical inquiries, systematic reviews (SRs) deliver the highest level of evidence in medical sciences.1 They can cover a variety of domains, including treatment and diagnostics. Presenting a full overview of the literature and delivering an unbiased estimate of effect are key aims of SRs. In this editorial, we explore publication bias, one of the potential sources of bias in SRs.

Publication bias: is a PubMed search enough?

Authors of SRs usually search multiple databases to find relevant publications. However, is all the available evidence identified with this approach? Publication bias is one threat to delivering an unbiased effect estimate.2 ,3 Publication bias is a phenomenon where journals are more likely to publish positive results, as these articles yield more citations. Non-significant publications are more prone to be rejected and remain unpublished.4 Unpublished resources are known as ‘grey literature’.

Publication bias has been shown in …

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  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.