Crossmatching either by complement-dependent cytotoxicity (CDC) and/or by flow cytometry (FCXM) are routinely used for assessing anti-HLA donor antibodies before kidney transplantation. FCXM has demonstrated greater sensitivity and many transplant centers have opted for its use without the concomitant CDC assay. The objective of this study was to evaluate the accuracy of the median channel shift (MCS) in the FCXM in predicting the CDC assay results. A total of 1516 T cell FCXM and 1408 B cell FCXM were studied in deceased donors lymphocytes between January/2016 and March/2017. The high detection rate of CDC+ results by FCXM+ resulted in 87% (FCXM-T) and 90% (FCXM-B) sensitivity, and 98% negative predictive value, for both. The low specificity of FCXM B (43%) is atributed to cases of CDC-/FCXMB+. FCXM T and B were able to detect 53% and 76% of cases with donor specific antibodies of classes I and II with intensity of fluorescence ≥5001. The MCS differentiated CDC+ (Md, P25 and P75) results: MCS-T 390 (245-469) and MCS-B 282 (180-350). Through ROC curve analysis (AUC), the MCS showed satisfactory performance in detecting CDC+: MCS-T 0.909 (0.886-0.933) and MCS-B 0.775 (0.724-0.826). Considering the accuracy and sensitivity evaluation, the MCS-T 245 and MCS-B 282 cutoffs showed a better prediction of CDC+. This study showed that it is possible to calibrate MCS based on CDC+ with accuracy >90%, however, that leads to a risk in terms of non-detection of low-titer anti-HLA antibodies.
Keywords: Flow cytometry; Kidney transplantation; Median channel shift.
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