Intended for healthcare professionals


The risk of bias from omitted research

BMJ 2000; 321 doi: (Published 07 October 2000) Cite this as: BMJ 2000;321:845

Evidence must be independently sought and free of economic interests

  1. Silvio Garattini (, director,
  2. Alessandro Liberati, associate professor
  1. Istituto di Ricerche Farmacologiche “Mario Negri,” Via Eritrea 62, 20157 Milan, Italy
  2. Centro Cochrane Italiano, Istituto di Ricerche Farmacologiche “Mario Negri,” Via Eritrea 62, 20157, Milan, Italy and Università di Modena e Reggio Emilia, Via Campa 287, Modena, Italy

    The rise of evidence based health care has highlighted the use of ineffective interventions, the risks of uncoordinated research, and the consequences of relying on studies published in prestigious journals while ignoring unpublished ones that have negative findings.1-5 Systematic reviews of the best evidence are now recognised as fundamental tools in overcoming these problems because they highlight questions that need urgent answers.6 But is evidence based health care achieving its goals? Aren't systematic reviews which are based on existing research at risk of amplifying the irrelevant? Should we be more concerned about “bias caused by omitted research” than the well recognised pitfall of publication bias?

    The increasing awareness of this danger is leading to efforts to correct this imbalance. One such attempt is the Cochrane Collaboration (an international organisation named after Archie Cochrane, the British epidemiologist), which is committed to preparing, maintaining, and disseminating systematic reviews to map the value of healthcare interventions.7 The public and the media are attracted to alternative medicine, while doctors, who often criticise the use of these unproved …

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