Pretransplant donor-specific antibodies detected by single-antigen bead flow cytometry are associated with inferior kidney transplant outcomes

Background. The clinical significance of pretransplant donor-specific antibodies (pre-Tx DSAs) detected by single-antigen bead flow cytometry (SAB-FC) remains unclear. Methods. To investigate the impact that pre-Tx DSAs detected by SAB-FC have on early clinical outcomes, we tested pre-Tx sera from all consecutive deceased-donor kidney transplants performed between January 2005 and July 2006 (n=237). Results. In the study population of which 66% had ahigh-immunologic risk, mean fluorescence intensity (MFI) more than or equal to 100 for class I and more than or equal to 200 for class II were the lowest DSA thresholds associated with inferior antibody-mediated rejection-free graft survival (75% vs. 90%, P=0.004 and 76% vs. 87%, P=0.017, respectively). The hazard ratio for antibody-mediated rejection increased linearly with higher class II DSA from MFI 100 to 800 (1.7[0.8-3.2], P=0.1 for MFI≥100 vs. 4.7[2.4-8.8], P<0.001 for MFI ≥800). Differences in graft function were only evident in patients with class II MFI more than or equal to 500 (estimated glomerular filtration rate: 47.6 vs. 54.3, P=0.02 and proteinuria: 0.6±0.6 vs. 0.4±0.3, P=0.03). A difference in death-censored graft survival was detected in patients with class II MFI more than or equal to 1000 (75% vs. 91.9%, P=0.055). Conclusion. High-pre-Tx DSAs detected by SAB-FC are associated with incrementally poor graft outcomes in deceased-donor kidney transplant with high-immunologic risk.