QQ plot for the genome-wide association of anti-PF4/heparin antibodies for discovery cohort (A) and replication cohort (B). QQ plots were generated from the primary GWAS analysis results. P values were generated using multivariate linear regression adjusted for age, sex, and principal components 1 to 3 in an additive model. Observed P values on the −log₁₀ scale are plotted on the left vertical axis, and expected P values on the −log₁₀ scale are plotted along the horizontal axis.