This is an archived version of the Handbook. For the current version, please go to training.cochrane.org/handbook/current or search for this chapter here.

There are four widely used methods of meta-analysis for dichotomous outcomes, three fixed-effect methods (Mantel-Haenszel, Peto and inverse variance) and one random-effects method (DerSimonian and Laird). All of these methods are available as analysis options in RevMan. The Peto method can only pool odds ratios whilst the other three methods can pool odds ratios, risk ratios and risk differences. Formulae for all of the meta-analysis methods are given by Deeks et al. (Deeks 2001).

Note that zero cells (e.g. no events in one group) cause problems with computation of estimates and standard errors with some methods. The RevMan software automatically adds 0.5 to each cell of the 2×2 table for any such study.