Intended for healthcare professionals

Endgames Statistical Question

Meta-analyses V

BMJ 2011; 342 doi: (Published 09 February 2011) Cite this as: BMJ 2011;342:d686
  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 analgesic effect of acupuncture.1 Randomised controlled trials of acupuncture for pain were included only if they had three arms incorporating two control groups, with patients randomised to acupuncture, placebo acupuncture, or no acupuncture. Thirteen trials were indentified. Placebo acupuncture included insertion of needles into non-acupuncture points or the use of non-penetrating needles. Separate analyses were undertaken for acupuncture versus placebo acupuncture and placebo acupuncture versus no acupuncture.

The trials used different instruments to record the primary outcome of self reported pain at the end of treatment, including visual analogue scales and ranking scales. Therefore, standardised mean differences were calculated. The results of the meta-analysis for acupuncture compared with placebo acupuncture were presented in a forest plot (figure).

Forest plot of the effectiveness of acupuncture compared with placebo acupuncture in reducing pain at end of treatment. For each trial and the total overall effect, the mean difference in pain was derived as acupuncture minus placebo acupuncture …

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