In general, a majority of meta-analyses of gene effects conducted by GENEVA groups have adopted a fixed-effects model, with selective testing for random-effects in subsequent follow-up analyses. Kraft, Zeggini & Ioannidis [Kraft et al., 2009] provide evidence for reduced power and deflation of the heterogeneity parameter in standard meta-analyses – hence, heterogeneity testing is restricted to the most promising signals.
