Clinical Trials

❘❙❚■ Chapter 38 | Meta-AnalysisFigure 1. Funnel plot of the data from the 14 trials displayed in Table 1. The plot resembles a symmetricalinverted funnel, suggesting no publication bias in this meta-analysis.4,0003,5003,000Sample size (subjects)2,5002,0001,5001,0005000| | | | | | |0 0.2 0.4 0.6 0.8 1.0 1.2 1.4Odds ratiostudy duration, and primary and other outcomes should be extracted in a standardform to be used for further statistical analysis.Step 5: Statistical analysisThe final step of a meta-analysis is to combine the information from thedifferent studies by employing appropriate statistical methods to enableinterpretation of the pooled effect. This combination might take place at the levelof individual patient data or at the level of aggregate trial results and outcomes ofinterest. There are two basic data requirements for a meta-analysis of aggregatetrial results:• A common measure of treatment effect, such as OR, risk ratio, or meandifference, must be used to compare the different treatment strategiesused in each study.• The variance (or standard error) of the treatment effect must becalculated for each study.In the beta-blocker study example, the measure of the chosen treatment effect wasthe OR for the mortality of patients on beta-blockers versus placebo, a commonlyused statistic [8].444