Detection of donor-specific antibodies using HLA-coated microspheres: another tool for kidney transplant risk stratification

Background. Sensitive techniques are able to detect low levels of circulating antibodies. For many newer techniques, the clinical consequences of these antibodies are unknown. We hoped to determine the significance of antibodies detected through the use of Luminex (R) microsphere-based assay. Methods. Patients who received kidney transplants between March 2003 and May 2004 with negative anti-human globulin-augmented complement-dependent cytotoxicity (AHG-CDC) crossmatches were retested for pre-transplant panel reactive antibodies (PRA) using Luminex microspheres and stored sera. Patients were considered to have circulating antibodies if either class I or class II Luminex PRA was >= 15%. These patients were then analysed for pre-transplant donor-specific antibodies (DSA). Clinical outcomes were compared in patients with and without DSAs. Results. Out of 136 patients who underwent transplantation, 55 had Luminex PRA >= 15%. Of these 55 patients, only 16 had a standard PRA >= 30% and 75% had a history of a sensitizing event. Twenty out of 55 patients were DSA+. Patients with DSA detected by Luminex had higher rates of primary non-function (PNF), delayed graft function, biopsy-proven acute rejection, and lower rates of graft survival at 6 months. A combined endpoint of immunological and clinical events was far more common in patients with DSA. Conclusion. The detection of DSAs by Luminex microspheres was associated with significantly higher rates of graft dysfunction and immunological events. Conversely, the presence of antibodies but no DSA by Luminex was associated with excellent outcomes. In patients with negative AHG-CDC crossmatches, the occurrence of low-level DSA by Luminex could assist in identifying patients that require more aggressive immune monitoring or immunosuppressive strategies.