Intended for healthcare professionals

Endgames Statistical Question

Meta-analyses: sources of bias

BMJ 2011; 343 doi: (Published 17 August 2011) Cite this as: BMJ 2011;343:d5085
  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 undertook a meta-analysis of the effectiveness of parenteral corticosteroids for the relief of acute severe migraine headaches and prevention of recurrent headaches in adults. Seven randomised placebo controlled trials were identified in which single dose parenteral dexamethasone was given in combination with standard abortive treatment.1

Dexamethasone and placebo were found to provide similar acute pain relief. Dexamethasone was, however, reported to be more effective than placebo in preventing recurrent headaches within 72 hours (relative risk 0.74, 95% confidence interval 0.60 to 0.90).

Which of …

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