48-P

Abstract

Virtual crossmatches (VXM) are used by transplant programs to evaluate compatibility with potential donors using a recipient’s HLA antibody profile and donor HLA typing. The aim of this study was to determine if the MFIs of single antigen donor specific antibodies (DSA) could be used to predict flow cytometric crossmatches (XM). Patient samples were screened for antibodies to mismatched donor antigens using Luminex single antigen (LSA) beads. The LSA bead MFI values were then correlated with the XM value. Only single antigen DSA was used for this study. Patients with anti-Cw or anti-DP antibodies and MFI values on beads known to give false positive results were also removed. The mean LSA bead MFI values of the recipients correlated with their XM values ( r 2 = 0.81 for class I DSA; r 2 = 0.75 for class II DSA). A significant difference between the DSA MFI values in patients whose XM was weak versus strong was found for both class I and class II antibodies. A cutoff MFI value of ⩾2000 predicted 100% of the moderate and strong XMs for both class I and class II antibodies. A prospective XM would be recommended for LSA bead MFI values from 1000-1999 (grey zone). [Fig. 1] A patient’s DSA profile can be used for a VXM and its predictive power is better when the LSA MFI is higher. Single antigen DSA MFI values can be used to predict moderate and strong XM. Further analysis of multiple DSA with VXM needs to be performed.