For each locus (HLA‐A, ‐B, ‐DR, and ‐DQ), chi‐square testing demonstrated highly significant variation among ethnic groups ( p < 0.001), validating that the observed disparities in mismatch exposure were statistically robust.
Among the Black subgroup, the analysis revealed that donor‐recipient mismatches in the DR category were associated with reduced sub‐distribution hazard ratios (SHRs), specifically, a SHR of 0.693 (95% CI: 0.432, 1.113) for Level 2, however, it did not reach statistical significance ( p = 0.129).