Preoperative Evaluation of Sensitized Patients

Since donor-specific antibodies (DSA) can induce antibody-mediated rejection in renal allograft, it is important to characterize HLA antibodies of the patient. Various tests are performed to detect HLA antibodies, but each test has its own limitations. Complement-dependent cytotoxicity (CDC) can detect complement-fixing antibodies, but it can be affected by drugs and non-HLA antibodies. Flow cytometry crossmatch (FCXM) detects HLA antibodies with greater sensitivity than CDC, but it cannot distinguish cytotoxic and noncytotoxic antibodies, and can be affected by nonspecific binding of non-HLA antibodies. Single antigen bead (SAB) assay has the greatest sensitivity to detect HLA antibodies. However, such low-titer HLA antibodies detected by SAB assay might not be clinically significant, and since HLA antigens are artificially attached to microbeads, false positive, false negative, or prozone effect can happen. Other kinds of solid phase assays, such as C1q SAB assay and C3d assay, are used to detect HLA antibodies, which can activate complement cascade. These HLA antibody assays should be interpreted in a comprehensive way.