Intended for healthcare professionals


Bridging the gaps in evidence based diagnosis

BMJ 2006; 333 doi: (Published 24 August 2006) Cite this as: BMJ 2006;333:405
  1. Sharon E Straus (, associate professor
  1. Department of Medicine, University of Calgary, Calgary AB, T2N 4N1

    Evidence on diagnostic accuracy and precision is scant and hard to find

    The process of diagnosis is complex and poses many challenges to doctors and other clinicians attempting to practise in an evidence based manner. When making a diagnosis in patients who are already ill we should be able to draw on evidence about the accuracy of diagnostic tests. When trying to make an early diagnosis of presymptomatic disease in well people through population screening we rely on evidence from randomised trials on whether patients benefit from such screening. Looking for presymptomatic disease among patients with an unrelated disorder (case finding) or trying to generate a differential diagnosis for patients' signs and symptoms require different types of evidence. We need to match each question to the type of evidence by using a diagnostic strategy.

    Furthermore, diagnosis seldom relies on a single test. Ideally a clinician would like to find valid evidence about a cluster of tests, including the clinical examination, along with measures …

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