Comparison of kidney transplant outcomes in HLA compatible and incompatible transplantation: A national cohort study

Background Reports of HLA incompatible (HLAi) kidney transplant outcomes are inconclusive, especially in the context of lower level Donor Specific Antibodies (DSA). Methods Multi-centre national cohort study of HLAi kidney transplant recipients matched in 1:2 ratio with HLA compatible (HLAc) kidney transplant recipients. HLAi defined as DSA identified by Luminex. Antibody mediated rejection (AMR) and transplant-survival were analysed using Kaplan-Meier plots. Propensity score (PS) matching was used to compare recipient and transplant survival between groups. Results We included 61 HLAi and 122 HLAc recipients; mean age 46 years; 60% female. MFIT0: 3327 (IQR 1352-6458), 23 (38%) were Flow cytometry crossmatch positive (FC-XMPOS). DSA(POS)/FC-XMPOS transplantation carried an increased risk of AMR at 1 year (52%) compared to DSA(POS)/FC-XMNEG (27%) and HLAc (0%). Unadjusted death censored graft loss at 3 years was 13% (HLAi) and 8% (HLAc). Three-year patient survival was 95% in HLAc, 84% in DSA(POS)/FC-XMNEG and 69% in DSA(POS)/FC-XMPOS recipients; 58% of HLAi deaths were infection-related. HLA incompatibility was associated with a decreased 3-year survival in our PS-matched cohort. Conclusion In kidney transplantation, DSA and positive FC-XM carries an increased risk of AMR. Despite inferior transplant and survival outcomes compared to HLAc transplantation, it remains a realistic option for highly sensitized patients facing prolonged waiting times and reduced survival on dialysis.