Intended for healthcare professionals

Endgames Statistical Question

Screening tests: likelihood ratios

BMJ 2011; 342 doi: (Published 29 June 2011) Cite this as: BMJ 2011;342:d3986
  1. Philip Sedgwick, senior lecturer in medical statistics
  1. 1Section of Medical and Healthcare Education, St George’s, University of London, Tooting, London, UK
  1. p.sedgwick{at}

The accuracy of asking patients two questions as a screening tool for depression in primary care was assessed.1 The questions focused on depression and pleasure within the past month. Consecutive patients not taking psychotropic drugs who attended their general practice were invited to participate, of whom 421 agreed. Patients were asked the two questions at any time during their consultation, and if the response to either was positive then screening was considered “positive” and the patient deemed at “high risk” of depression; otherwise screening was considered “negative” and the patient deemed at “low risk” of depression. A self completed, computerised international diagnostic interview was used to diagnose depression.

The two questions showed a sensitivity of 97% and specificity of …

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