C1q Test for Identification of Sensitized Liver Recipients at Risk of Early Acute Antibody-Mediated Rejection.

BACKGROUND The majority of liver recipients transplanted with positive crossmatch have a post-transplant course free of acute antibody-mediated rejection (AMR). However, 10% of sensitized recipients develop early severe AMR. There is no clear strategy that would allow for predicting the postoperative course in sensitized liver recipients. One of the possible factors contributing to the dichotomous course in sensitized recipients may be the complement-binding characteristics of the donor-specific antibodies (DSA). MATERIAL AND METHODS We tested sera of sensitized recipients with DSA at the time of transplant, diagnosed with severe AMR or 'AMR-free' for C1q reactivity and strength of mean fluorescence intensity (MFI) in single-antigen beads (SAB) assay. RESULTS Both groups tested positive for DSA C1q binding and DSA-SAB. Recipients with early AMR had significantly stronger DSA MFI in the C1q assay (P<.0001). AMR was observed in patients with very high DSA C1q MFI (22681±8841 vs. the no-AMR group 7954±2061). In SAB assay, DSA MFI strength differences were equivocal (P=0.31). CONCLUSIONS The C1q test is a supportive adjunct in identifying patients at risk of postoperative acute AMR and selects an AMR-free course with 100% negative predictive value despite the presence of DSA.