Meta-analysis

It is common to find that several trials have attempted to answer similar questions about clinical effectiveness. Often many of the individual trials will fail to show a statistically significant difference between treatments. However, when the results from individual studies are combined using appropriate techniques (meta-analysis), significant benefits of treatment may be shown. Systematic review methodology is at the heart of meta-analysis.

(Crombie & Davies, 2009).

In summary:

• Meta-analysis is a statistical technique fro combining the findings from independent studies
• Meta-analysis is most often used to assess the clinical effectiveness of healthcare interventions; it dopes this by combining data from two or more randomised control trials
• Meta-analysis of trials provides a precise estimate of treatment effect, giving due weight to the size of the different studies included
• The validity of the meta-analysis depends on the quality of the systematic review on which it is based
• The Cochrane Collaboration provides Review Manager (RevMan) software that includes performing meta-analyses and presenting the results graphically.

Example of a published meta-analysis

Heneghan C, Alonso-Coello P, Garcia-Alamino JM, Perera R, Meats E, Glasziou P. Self-monitoring of oral anticoagulation: a systematic review and meta-analysis. The Lancet, 2006: 367: 404-411