ABO Genotyping finds more A2 to B kidney transplant opportunities than lectin-based subtyping
Abigail Joseph, Cody Murray, Natasha Novikov, Randall W. Velliquette, Sunitha Vege, Justin B.L. Halls, Helen Mah, Jamie L. DellaGatta, Edward Comeau, Maria Aguad, Richard M. Kaufman, Martin L. Olsson, Indira Guleria, Sean R. Stowell, Edgar L. Milford, Annika K. Hult, Melissa Y. Yeung, Connie M. Westhoff, Cathi Murphey, William J. Lane
Abstract
ABO compatibility is important for kidney transplantation, with longer waitlist times for blood group B kidney transplant candidates. However, kidneys from non-A1 (eg, A2) subtype donors, which express less A antigen, can be safely transplanted into group B recipients. ABO subtyping is routinely performed using anti-A1 lectin, but DNA-based genotyping is also possible. Here, we compare lectin and genotyping testing. Lectin and genotype subtyping was performed on 554 group A deceased donor samples at 2 transplant laboratories. The findings were supported by 2 additional data sets of 210 group A living kidney donors and 124 samples with unclear lectin testing sent to a reference laboratory. In deceased donors, genotyping found 65% more A2 donors than lectin testing, most with weak lectin reactivity, a finding supported in living donors and samples sent for reference testing. DNA sequencing and flow cytometry showed that the discordances were because of several factors, including transfusion, small variability in A antigen levels, and rare ABO∗A2.06 and ABO∗A2.16 sequences. Although lectin testing is the current standard for transplantation subtyping, genotyping is accurate and could increase A2 kidney transplant opportunities for group B candidates, a difference that should reduce group B wait times and improve transplant equity.