Intended for healthcare professionals

Endgames Statistical Question

Number needed to treat

BMJ 2010; 341 doi: (Published 13 October 2010) Cite this as: BMJ 2010;341:c5614
  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}

Researchers compared the efficacy of foot orthoses with both flat inserts and multimodal physiotherapy in the management of patellofemoral pain syndrome. They used a single blind randomised controlled trial study design. A total of 179 participants were recruited and randomised to six weeks of physiotherapist intervention with off the shelf foot orthoses, flat inserts, or multimodal physiotherapy.1

Primary outcome measures included self assessment of change in pain at six weeks from baseline. Each participant recorded self perceived change in pain on a five point Likert scale (categorised as “marked improvement,” “improvement,” “neither improvement nor worsening,” “worsening,” or “marked worsening”). Global improvement was considered to be self reported marked or moderate improvement in pain.

At six weeks, a greater proportion of those allocated foot orthoses reported global improvement compared with those allocated flat inserts (85.4% v 57.5%), giving a relative risk of …

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