P038 Donor specific anti-a titer for abo incompatible (ABOi) living kidney transplantation

To increase the donor options for our active living kidney donor program, candidates who are blood group B may receive a living donor transplant from a non-A1 or non-A1B donor. ABO incompatible donors (ABOi) are no longer an absolute contraindication for kidney transplantation as long as the recipient titer against ABO A is low. It is well known that there are several variations of non-A1 blood groups, and therefore measurement of anti-A titer against commercial A1 or A2 cells may not provide an accurate measurement of donor reactive IgG antibody to blood group A antigens. Therefore, we have initiated a strategy of assessing anti-A titers using red cells from the prospective non-A1 donor being evaluated. The candidate will have initial non-A1 titers performed with commercially produced A2 red cells as well as red cells from the intended living donor. This will help identify the rare instance of a more or less immunogenic ABO A subgroup. Recipient sera is serially diluted with saline from 1:1 to 1:32 in a standard tube assay. One drop of RBC suspension (50 ul) is added to 2 drops (100 ul) of each sera dilution. Tubes are incubated at RT for 30 min, centrifuged and agglutination macroscopically observed and recorded. This provides measurement of the IgM non-A1 titer present in the recipient. Tubes are then incubated at 37C for 30 min, washed 4 times with saline, IgG added, then centrifuged and agglutination recorded again to provide IgG non-A1 titer results. To be considered compatible for non-A1 or non-A1B donors, the IgG titer obtained with A2 reagent cells should be no higher than 1:16, and no greater than 1:8 with the intended living donor. Titers must be repeated within 48 h prior to transplant. Consistent with initial testing, IgG non-A1 titer results at the time of transplant are considered acceptable if the titer is no greater than 1:16 against commercial A2 red cells, and 1:8 against the red cells of the intended deceased donor. As of the date of this submission we have performed two such ABOi transplants using this testing methodology, with no rejection episodes occurring thus far.