an omnibus test for effect in any tissue while accounting for correlation57,58. Though the correlation observed in our data was almost entirely driven by the YFS:NTR blood datasets, we expect this to be an especially useful strategy for future studies with many correlated tissues. An alternative approach would be to perform traditional meta-analysis across the three cohorts and then predict the TWAS effect. However, this would lose power when true eQTL effect-sizes (or LD) differ across the cohorts, which we have empirically observed to be the case looking at predictor correlations above. The proposed omnibus test aggregates different effects across the studies, at the cost of additional degrees of freedom.
