with PRS-CSx trained on UKBB and BBJ GWAS only, suggesting that PRS-CSx benefits from including samples that have matched ancestry with the target population in the discovery dataset, even if the non-European GWAS included are considerably smaller than European studies (Fig. 3c; Supplementary Tables 14). We note, however, that the overall prediction accuracy in the AFR population remained low relative to the predictions in EUR and EAS individuals, reflecting highly imbalanced sample sizes in the training GWAS across populations (Extended Data Fig. 8). We additionally assessed the convergence of the model fitting algorithm used in PRS-CSx, and confirmed that the Gibbs sampler achieved reasonable convergence and mixing38 (Supplementary Note; Extended Data Fig. 9).
