There were two fascinating talks about the use of C1q modified Luminex assay to assess for complement fixing antibodies both before and after kidney transplantation. Prior studies, including one published in the NEJM, suggest that C1q fixing antibodies after kidney transplant are predictive of poor graft survival, while C1q negative antibodies are not. In the NEJM study there was a question as to whether these antibodies were C1q binding simply because they were present in higher concentration. Dr. M. Ajaimy from Montefiore, New York, presented a study which confirmed the above NEJM study findings. Development of de novo C1q antibodies in their study predicted poor outcome and a higher incidence of antibody mediated rejection. C1q fixing HLA class 1 antibodies were found to have a higher concentration (as suggested by higher mean fluorescent intensity) than C1q negative antibodies while there was no significant difference in antibody concentration for C1q positive vs. C1q negative HLA class II antibodies. The next study, as presented by Dr. P. Amico from Basel, looked at the effect of pre-transplant C1q binding antibodies on post-transplant outcomes. In stark comparison to the prior study they found that C1q fixing antibodies were not better at predicting outcome than non C1q fixing antibodies when accounting for antibody strength (MFI). They found a very strong association between C1q fixing ability and antibody strength suggesting that there is no added benefit from performing the C1q assay. So is the C1q assay useful or not? So far the evidence for testing post-transplant is gaining momentum while pre-transplant testing is not. Whether this assay adds additional value to standard assessments of antibody strength is still unclear.
Post written by Dr. Vinay Nair, AJKD Blog Advisory Board member.
Check out more AJKD blog coverage of the 2015 American Transplant Congress.