69-P

Abstract

Aim It is widely believed that complement fixing donor specific antibody is more clinically relevant than non-complement fixing antibody. However, the C1q assay, which is used to determine if there is complement fixing Donor Specific Antibody (DSA) is time consuming and expensive. We wanted to study if the Luminex Single Antigen (SA) MFI level is related to the presence of C1q fixing antibody. Methods Twelve kidney recipient sera, demonstrating a total of 29 anti-HLA DSAs by the SA assay (One Lambda, Canoga Park, CA) were tested by the C1q assay (One Lambda, Canoga Park, CA). Results Five of these sera demonstrated C1q fixing DSAs. The average MFI of the SA for these positive sera was 17,920. The average MFI of the SA for the sera not having C1q antibody specificities was 4776. There were three sera that had relatively high MFI values that were not positive by the C1q assay (MFI average 12,269) [Fig. 1]. Download full-size image Conclusions The strength of the MFI in classical Luminex SA testing has a high predictive value for positivity in the C1q assay. We found that sera with greater than 13,000 MFI by Luminex SA had a high probability of being positive by the C1q assay. Therefore, the use of the classical Luminex SA assay to determine the strength of the MFI is beneficial to determine if reflex C1q testing is warranted.