An auto-crossmatch can also be performed when troubleshooting unexpected reactivity from other methods. This procedure uses patient serum with patient cells. Auto-crossmatching can be done using flow cytometry, complement dependent cytotoxicity (CDC), or ELISA/solid phase methods.
Flow cytometry is the most sensitive method for crossmatching. It detects recipient IgG antibodies that have reacted with donor antigens on the surface of T and B lymphocytes. This uses anti-human globulin labeled with fluorescent dyes.
The graphic to the right shows a typical FXM. The x-axis represents the degree of fluorescence from labeled anti-human globulin bound to recipient/patient HLA antibodies that are already bound to donor lymphocyte HLA antigens. The y-axis is the number of cells. Movement up the y-axis and to the right on the x-axis are increasing values. Patient serum and donor lymphocyte values are compared to positive and negative control serum to determine positive or negative FXM.
14. Kentzel, Ethan. "Flow Cytometry Crossmatching (FXM) visual." 16 Apr 2021.
