Analysis of Positive Flow Cytometric Crossmatch in Organ Transplantation

ABSTRACT

BACKGROUND: Pretransplant HLA crossmatch is one of the most important parts in solid organ transplantation. Flow cytometic crossmatch (FCXM) is more sensitive than anti-human globulin enhanced complement dependent lymphocytotoxicity (AHG-CDC) in detecting anti-HLA antibodies. We compared the results of the two methods and analyzed the FCXM-positive cases in various aspects. METHODS: Sera from 212 patients were tested for the detection of anti-HLA antibodies by FCXM and 188 of them were also tested by AHG-CDC assay. The results were analyzed in relation to their histories of pregnancy, transfusion or organ transplantation and also according to the donor patient relationships. We compared the FCXM results obtained before and after desensitization therapy (using plasmapheresis and anti-CD20 antibody) in 5 sensitized patients. RESULTS: Concordance of the results between the two methods was 88.8% (167/188). FCXM results correlated with history of pregnancy, but not with that of transfusion. When the patients were divided into 4 groups according to donor-patient relationships, the T cell FCXM mean fluorescence intensity (MFI) ratio (sample/control) was significantly higher in the husband-to-multiparous wife group compared to the other 3 groups (children-to-mother, unrelated donor-to-multipara, and the rests). After desensitization therapy, MFI ratios of T cell FCXM decreased and those of B cell FCXM increased, probably due to rituximab effect, in all 5 patients. CONCLUSIONS: FCXM using a MFI ratio, has a higher sensitivity than AHG-CDC in detection of donor specific antibodies. Also it can be useful in monitoring antibody levels during desensitization therapy.