Background:

Blood group B patients are eligible to receive offers from non-A1 or non-A1B kidney donors. Current practice in many institutions involves performing these titers with A1 reagent cells. Since non-A1 cells express weaker antigenicity than A1 cells, the question was, “Why would surrogate ABO titer testing include target cells with higher antigenicity than the donor organ?” It is important to correctly subtype the donor using a pre-transfusion blood sample per UNOS standards. A titer at the time of organ offer using the donor cells, as well as the reagent cells is critical.

Study Design:

A comparison was done to determine the significance of A1 versus non-A1 titers in potential “non-A1/non-A1B donor to B patient” transplants. Parallel ABO titer testing was performed on 63 patients' samples using both A1 and non-A1 reagent cells. Pre-transplant titers were performed using donor cells, non-A1 reagent cells, and A1 reagent cells on 17 sample sets at the time of organ offer. Post-transplant outcomes were analyzed on 16 patients.

Findings:

Observations in blood group B patients (n=63) were: (a) the average of A1 Pre-transplant IgM results was 3.0 times higher than the average of non-A1 Pre-transplant IgM results [55/18], (b) the average IgM score of A1 was 1.6 times higher than the average IgM score of non-A1 [57/34], (c) the average of A1 Pre-transplant IgG results was 4.3 times higher than the average of non-A1 Pre-transplant IgG results [43/10], (d) the average IgG score of A1 was 2.1 times higher than the average IgG score of non-A1 [46/22].

Post-transplant data was received on 16 blood group B patients who received non-A1 kidneys with a low titer using non-A1 reagent cells (≤4), a higher titer using A1 reagent cells (>4), and a low titer using non-A1 donor cells (≤4); 15 are doing well, 1 patient passed away one month post-transplant with unknown cause of death.

Conclusions:

Blood group B patient titers against non-A1 reagent cells or non-A1 donor cells were generally low. As expected, A1 titers were generally higher. If A1 titer results were used by transplant centers for prequalification of the patient's inclusion in the “non-A1/non-A1B donor to B patient” transplant program, these patients would have been excluded. Based on our findings, we conclude that the results of using A1 titers for B patients receiving non-A1 kidneys are not clinically significant.

CITATION INFORMATION: King D, Aguilucho M, Marchioni M, Figueiredo B, Okere I, Rao P. Titers of Blood Group B Patients Using Non-A1 Reagent/Donor Cells for the Purpose of ABO Incompatible Kidney Transplantation. Am J Transplant. 2017;17 (suppl 3).

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