Clinical Significance of Flow Cytometry in Solid Organ Transplantation

Detection of circulating anti-HLA antibodies in the serum of a solid organ recipient is generally considered to be a strong contraindication to a successful transplantation. For several years, the only test available to detect such antibodies has been the complement-dependent lymphocytotoxicity (CDC) assay. However, the test is not sensitive enough to detect low titer anti-donor antibodies that may still cause accelerated graft rejection. The test is also grossly unsuitable for patients requiring a re-graft. Further, the test is associated with the usual complement-associated problems leading to false-negative or false-positive results. Over the years, the flow cytometric crossmatch (FCXM) which is 10–100-fold more sensitive than the CDC assay has globally emerged as the test of choice for most transplant centers. The test is important for identifying sensitized patients waiting on dialysis as well as for those requiring a second graft. Such patients have a difficult post-transplant course, often leading to rejection. This chapter describes the basic principle of the FCXM test, instrumentation required by the laboratory along with the desired expertise of the personnel, the exact procedure to be followed, and possible limitations of the test. An important requirement is the correct interpretation of the test results for efficient clinical management.