- a positive crossmatch requiring pretransplant desensitization (defined as a positive T-cell FCXM of greater than or equal to 300 but less than 450 prior to desensitization, or as a positive B-cell FCXM of > 300 but < 450 prior to desensitization with demonstrable Class II DSA on solid-phase assays). Subsequent to desensitization, patient must have, at the time of transplant, a T-cell and B-cell FCXM less than 300; or