This workshop is given on behalf of the Statistical Methods Group.

Workshop type: Training.

Objective: To provide review authors with the knowledge to perform meta-analysis with dichotomous outcome data, and to understand the implications of choosing different effect measures.

Summary:
Dichotomous data are perhaps the most common type of outcome in studies included in Cochrane reviews. However, there a several ways in which a simple 2x2 table from an individual clinical trial can be analysed, and even more ways in which results may be combined across studies in a meta-analysis.

This workshop will review the notions of risk and odds, and of risk ratio, odds ratio, risk difference and number needed to treat. It will then discuss the relative merits of the different effect measures, including the implications of swapping interest from ‘events’ to ‘non-events’.

A simple o verview of the different methods for combining results in meta-analysis will be provided (including the Peto method, Mantel-Haenszel methods and inverse-variance method). Note that the last of these is newly implemented in RevMan 5, and the rationale for including it will be discussed.

Issues will be illustrated by examples. Time will be allowed for discussion of the issues raised.

 [The workshop is part of a series of five workshops on meta-analysis, but does not require attendance at any of the others in the series.]

Intended audience: Review authors.

Technical level expected of participants: Basic.