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Understanding randomised controlled trials
  1. A K Akobeng
  1. Correspondence to:
    Dr A K Akobeng
    Department of Paediatric Gastroenterology, Central Manchester and Manchester Children’s University Hospitals, Booth Hall Children’s Hospital, Charlestown Road, Blackley, Manchester, M9 7AA, UK;


The hierarchy of evidence in assessing the effectiveness of interventions or treatments is explained, and the gold standard for evaluating the effectiveness of interventions, the randomised controlled trial, is discussed. Issues that need to be considered during the critical appraisal of randomised controlled trials, such as assessing the validity of trial methodology and the magnitude and precision of the treatment effect, and deciding on the applicability of research results, are discussed. Important terminologies such as randomisation, allocation concealment, blinding, intention to treat, p values, and confidence intervals are explained.

  • CONSORT, consolidated standards of reporting trials
  • EBM, evidence based medicine
  • PCDAI, paediatric Crohn’s disease activity index
  • RCT, randomised controlled trial
  • evidence based medicine
  • hierarchy of evidence
  • randomised controlled trial
  • random allocation
  • critical appraisal

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  • Competing interests: none declared