P047 Stability of anti-A2 blood group subtype titers among blood group B candidates

Abstract

Aim Kidney allocation based on blood type inadvertently disadvantages ABO B blood group candidates due to their disproportionate representation on the waitlist. To mitigate this situation, OPTN/UNOS modified the allocation system such that group B candidates could receive kidneys from group A2 or A2B donors if their anti-A titers are Methods Anti-A titer information and candidate demographics were reviewed from blood bank records. Patients included in the study were group B, renal allograft candidates who had ⩾2 anti-A titers performed between January 2011 and December 2014. An anti-A titer of >1:8 excluded a group B candidate from receiving an out of group allograft. Variability in titers was assessed by delta dilution change between assays. Results Anti-A titers were assessed on 193 group B, renal allograft candidates with ⩾2 anti-A titers. Following the first titer, 50 patients (26%) were ineligible (i.e.,titer >1:8). Of the remaining 143 patients, 19 (13%) became ineligible following a second titer reaching >1:8. Forty patients (28%) had no delta dilution change between titers and 72 (50%) had a titer change that never reached >1:8. Only 12 patients (6% of total) experienced a titer change that affected eligibility after the second test. Conclusions Although the majority of patients experience some variability in their anti-A titers over time, in most cases the variability does not affect their eligibility to receive an out of blood group renal allograft. Furthermore, the likelihood of a titer change affecting eligibility after two tests is limited to a small subset of patients. Our data suggest that testing of anti-A titers more than twice may not be necessary to effectively monitor recipient eligibility.