The approach to preoperative crossmatch-positive patients for living donor renal transplantation is difficult because the presence of preformed donor-specific antibodies (DSA) and crossmatch test results can be inconsistent; consequently authenticity of the test results and immunological background must be carefully considered in each case. In this study, we investigated the presence of DSA, desensitization therapy, rejection, postoperative DSA status, and transplant renal function in living donor renal transplant recipients with positive preoperative flow cytocross-match (FCXM) results.
Of the 195 living donor renal transplant cases performed in our department since 2016, 32 showed preoperative FCXM positivity. Nine cases were positive only for FCXM-T, which is theoretically considered a technical error; however, preformed DSA were not detected in all the cases. Six patients had incompatible blood groups; one patient had a history of massive blood transfusion during aortic valve replacement and one patient had anti-mitochondrial antibodies, which may have generated the technical error of FCXM-T-only positivity. All the patients were alive and progressed without de novo detection of DSA.
Only 17 patients were positive for FCXM-B . Of these, only 2 had preformed DSA: one patient exhibited hyperacute antibody-associated rejection related to an ABO-incompatible transplant, while the other had no DSA or immunological events. Fifteen patients without preformed DSAs generally did well; however, one case of de novo DSA was detected 2.4 years later, and chronic active antibody-associated rejection was observed.
Six patients tested positive for both FCXM-T and FCXM-B. No preformed DSA were detected in two cases, although theoretically, DSA for HLA class I should have been detected. In addition, in two cases preformed DSA were not detected for HLA class I, and in one case DSA were not detected for HLA class II. Despite inconsistencies in the FCXM results, preoperative desensitization therapy was administered, which included rituximab, plasma exchange, and high-dose γ-globulin therapy. One patient underwent transplant nephrectomy for non-immunological reasons, but the other five patients successfully underwent transplantation.
Interestingly, most of the FCXM-T-positive patients who underwent living donor renal transplantation in our department were blood group-incompatible, and the results were more inconsistent than expected due to technical errors. Thus, if appropriate desensitization therapy can be implemented by fully considering the immunological background, patient burden can be reduced and medical resources can be conserved.