49 Supporting ABO Incompatible transplantation: Validating Dithiothreitol Anti-A Titers

In 2014, the Organ Procurement and Transplant Network (OPTN) permitted the allocation of A2 and A2B kidneys to group B candidates with low anti-A titers to increase access. To determine recipient eligibility, the OPTN requires anti-A titers with transplant centers determining eligibility titer cutoff. Historically, blood banks have performed antibody titers using AHG (AHG titers). However, titers for these types of transplants are routinely performed with Dithiothreitol (DTT)- treated serum (DTT titers). DTT disrupts IgM’s disulfide bonds; as such, reactivity is attributed solely to IgG. It was this method that was described in seminal literature of A2/A2B to B transplants. Consequently, the transplant program requested DTT titers to evaluate out-of-group eligibility; thus, the aim herein is to describe our experience transitioning from AHG titers in tube to DTT titers in tube. Validation was performed using serum from twenty group B transplant candidates. For AHG titers, plasma and A1 red cells were incubated for 60 minutes at 37 °C followed by AHG after washing. For DTT titers plasma was treated with 0.01 M DTT followed by a 10-minute, room temperature incubation with A1 red cells. Titers were completed using serial titration up to a 1:32 dilution. Titers <8 were considered eligible for an A2 transplant. We then compared our results to a comparator lab, which ran the samples using our protocol. DTT titers were also performed at dilution 1:8, with a titer < 8 indicating eligibility for an out-of-group transplant. Overall, the tube DDT titers resulted in lower titers compared to tube AHG titers (18/20; 90%). Interestingly, of the 10 samples that were ineligible by AHG, 5 became eligible by DTT. The correlation of tube DTT titers performed in our laboratory and the comparator laboratory was high (90%), and those that differed did not impact the eligibility status. The correlation between running a full serial tube titration and a single titration performed at the 1:8 cut-off dilution also had a high correlation of 95%. In summary, tube DTT results were expectedly lower than AHG tube titers, which could lead to increased eligibility and access to transplant for group B transplant candidates. The study with the comparator lab demonstrated high correlation, helping to validate the DTT titer method. Additionally, DTT results performed at one dilution (1:8) appeared equivalent to serial titration to determine eligibility. Performing titers at a single dilution would help with workflow, given the time it takes for manual tube titrations. Moving forward, we plan to evaluate this procedure for group O transplant candidates.