How is a living kidney donor evaluated to be compatible for a specific recipient? If not compatible, what options are available?
The evaluation of a potential living kidney generally begins with an assessment of the donor and recipient blood groups and a cross-match.
- • The donor and recipient generally must be ABO compatible. This can occur under one of the following circumstances: the donor and recipient are ABO identical, the donor has blood type O (universal donor), or the recipient is blood type AB (universal recipient). Given the distribution of blood group antigens in the United States, the waiting time on the deceased donor list is prolonged for patients with blood group O and B. A recipient with blood type B and a low anti-A Ag IgG titer can potentially receive a transplant from a donor with blood type A2B or A2 (see Question 8).
- • When a potential donor is identified, a cross-match is performed prior to transplantation to evaluate for any evidence of preformed antibodies against the specific donor (human leukocyte antigens [HLA]) that could result in hyperacute and/or acute humoral rejection. A final cross-match using fresh serum is performed in all cases immediately preceding transplantation to ensure compatibility between the donor and recipient. The methods available for cross-match testing include: enzyme-linked immunosorbent assay, flow cytometry, complement-dependent cytotoxicity, and single antigen bead assay. Transplantation has been done with low-level pre-existing donor specific antibody (DSA); however, graft function tends to worsen quicker than in those without pre-existing DSA.
- • If the donor is incompatible with the recipient, then Kidney Paired Donor Exchange is the most common solution today; we will discuss this further in the next question. ABO-incompatible or cross-match positive transplantations following desensitization strategies have been performed successfully at some institutions.