2-P: IMPACT OF LISTING UNACCEPTABLE ANTIGNES BASED ON C1q POSITIVE IN PAIRED KIDNEY EXCHANGE PROGRAM

Aim The method of choice in most of the HLA laboratories for the identification of anti HLA antibodies is the solid phase assay Luminex technology. This method is very sensitive and it is being used for virtual crossmatching as well as for paired kidney exchange (PKE) programs. The most challenging factor for the paired kidney exchange programs is the high sensitization level of the listed couples determined by Luminex-IgG MFI. Now it is increasingly believed that the complement fixing donor specific antibodies (DSA) are the more clinically relevant than non-complement fixing antibodies. In this study we determined impact of using Luminex C1q instead of Luminex-IgG in the pool of the couples listed in our PKE program. Methods A cohort of 12 patients was chosen randomly from the total of 28 couples constituting our HLA incompatible PKE program. All samples were tested by Luminex-IgG and Luminex-C1q (One Lambda) for HLA class I and II antibodies. The unacceptable antigens listed in the PKE are those with more than 6000 MFI for HLA-A,B,DR and DQ. For HLA-C it was 10000 MFI. Results The percentage of complement fixing antibodies detected for HLA class I and II were 36% and 35% respectively. When the unacceptable antigens entered in the PKE program were those Luminex-IgG positive, there were no exchangeable pairs. However when the unacceptable antigens entered in the PKE program were only those C1q positive, we found four one-way exchangeable pairs. Conclusions Our data suggest that we should consider listing unacceptable antigens in the PKE program using the Luminex-C1q positive instead of Luminex-IgG positive. Listing unacceptable antigen in the PKE program solely based on Luminex-IgG will deprive many patients from being transplanted with compatible pairs.