observed differences in results are compatible with chance. I2 measures the percentage of variability in effect estimates that is attributed to heterogeneity rather than chance (28). Heterogeneity in GWA studies can be attributed to differences between the included studies such as different populations, different linkage disequilibrium patterns, different environmental exposures, different genotyping platforms and different imputation accuracies, or it may represent unexplained statistical heterogeneity (27, 40, 80, 103).
