Background: The traditional method for assessing HLA antibodies in recipient serum samples is the complement-dependent cytotoxicity testing (CDC). Recently, the highly sensitive microbead-based Luminex assay was introduced and can detect low levels of anti-HLA Abs.
Objective: To determine the impact of pretransplant donor-specific HLA antibodies (DSA) detectable by Luminex, despite a negative CDC crossmatch, on the outcomes of kidney transplantation. The correlation and cut-off value of panel reactive antibody (PRA) and DSA was also evaluated.
Methods: Pre-transplant sera from 116 kidney transplant recipients with a negative CDC crossmatch were assessed for donor-specific HLA antibodies by using Luminex single antigen beads. The patients received kidney transplants at Ramathibodi Hospital between January 2003 and December 2007. The results were correlated with kidney graft outcomes.
Results: DSA were found in 24.1% (28/116) of all recipients. Of the twenty-eight DSA positive patients, four developed antibody-mediated rejection (AMR) (4/28 = 14.3%). All these 4 patients had positive C4d staining in their biopsies. Of the eighty-eight DSA negative patients, two developed AMR (2/88 = 2.3%). The AMR occurred more frequently in the DSA positive group than in the DSA negative group (14.3% versus 2.3%. The patient and graft survival were similar in both groups. The strength of pre-transplant DSA was not associated with the incidence of rejection episodes.
Conclusion: There was a higher incidence of AMR in patients with pre-transplant DSA despite a negative CDC crossmatch. However, pre-transplant DSA detected by Luminex had no statistically significant impact on delayed graft function, patient survival and graft survival.