DSA and C1q assay in kidney post-transplant monitoring

Aim Predicting the risk of graft loss using C1q assay in the post-transplant DSA monitoring. Methods Retrospective review of post-kidney transplant patients who were tested for DSA after ABO compatible kidney transplantation with negative T and B lymphocyte crossmatch. Patients in post-transplant follow-up since 2007 were tested for donor specific HLA antibody (DSA) IgG class according to schedule by Labscreen phenotype beads/Single Antigen beads (SAB, One Lambda), and if detected, reflexed to C1q assay (One Lambda) since 2011. Results Of the 437 post-kidney transplant patients (range: 1–27 years post-transplant, mean 9.1 years), de novo DSA was detected in 74 (16.9%). C1q assay was performed in 50/74 DSA positive patients: Positive at least once N = 35 (70%) and Negative N = 15. DSA in 26 patients were tested for > 1 year; persistently positive C1q, N = 17, eventually became C1q negative N = 6, or became DSA negative N = 3. Overall, C1q positive DSA presented higher maximum MFI detected by both phenotype beads and SAB, and resulted in higher graft loss. C1q MFI was similar between graft lost and functional (defined by not on dialysis). Regardless of C1q status, graft loss was observed after month-to-years with DSA, indicating chronic antibody mediated rejection. Conclusions Patients with C1q positive DSA had higher MFI (IgG) levels and resulted in higher graft loss.