Pretransplant Donor-Specific Antibody Levels Stratification and Early Kidney Transplant Outcomes with Predominant Antithymocyte Globulin Induction.

OBJECTIVES: The impact of preformed donor -specific antibodies after kidney transplantation in Middle Eastern populations remains unclear. Here, we evaluated the association between pretransplant donor -specific antibody levels and early outcomes after kidney transplant and aimed to identify predictors of high -level donor -specific antibodies in a predominantly antithymocyte globulin -induced cohort. MATERIAL AND METHODS: This retrospective study included 260 kidney transplant recipients (2021 -2024 ) at a single center in Saudi Arabia. We stratified patients by pretransplant donor -specific antibody level: none, low -level ( <1000 mean fluorescence intensity ), and high -level (≥1000 mean fluorescence intensity ). RESULTS: Among 260 transplant recipients, 151 (58 % ) had pretransplant donor-specific antibodies (3.8 % had acute rejection, 4.6 % had graft loss, 3.1 % had mortality ). In multivariable analysis, recipients with median age 48.0 years (interquartile range, 35.0-61.5 y ) had higher HLA mismatches, and use of antithymocyte globulin induction was independently associated with high -level donor -specific antibodies. In multivariable Cox regression, HLA mismatches (hazard ratio 1.32; 95 % CI, 1.06 -1.65; P = .013 ), impaired graft function at 4 months (estimated glomerular filtration rate <60 mL /min /1.73 m ²; hazard ratio 6.09; 95 % CI, 2.14 -17.33; P = .001 ), and pretransplant diabetes (hazard ratio 3.25; 95 % CI, 1.01 -10.44; P = .048 ) were independent predictors of a composite outcome of acute rejection, graft loss, or death. Having pretransplant donor -specific antibodies, including high levels, was not independently associated with adverse outcomes (P = .85 ). High -level donor-specific antibodies showed a trend toward lower early survival, although no independent association was detected, and the study may have been underpowered to identify modest effects. CONCLUSIONS: Pretransplant donor -specific antibodies were common, with high levels correlating with broader sensitization. However, early graft dysfunction and HLA mismatches had a greater effect on adverse outcomes than preformed donor -specific antibodies. Widespread use of antithymocyte globulin -based induction may have mitigated the immunologic risk of donor -specific antibodies, contributing to favorable early graft and patient outcomes.