Fig. 5. The addition of imputed C4A copy number to the association model reduces the observed signal below the genome-wide threshold suggesting its role as the candidate gene in the loci.

a Despite losing 14 cases due to the inability to impute C4A and C4B copy number, a genome-wide significant association is still observed on 6p21.32. b The addition of imputed C4B copy number to the association model still produces a robust genome-wide significant association, whereas adding imputed C4A copy number (c) results in a non-statistically significant association, suggesting that imputed C4A copy number is influencing the signal.