Becoming a chef in the human leukocyte antigen kitchen: Interpretation and modification of human leukocyte antigen-antibody assays

Purpose of review: Fluorescence-based human leukocyte antigen (HLA) antibody detection methods, including flow cytometric crossmatch and single antigen bead assays revolutionized HLA antibody identification and assessment of immunological risk in transplant candidates and patients. Nevertheless, these assays are not flawless and their interpretation can be complex. This review highlights the limitations of the single antigen bead and flow cytometric crossmatch assays and discusses protocol modifications and interpretive approaches to address these issues. Recent findings: Several limitations of HLA antibody detection methods have been identified in recent years. Protocol variability, denatured epitopes, and interfering factors can all significantly impact the identification of clinically relevant HLA antibodies. A number of solutions to address these challenges have been developed. These include pretreatment of sera, method standardization, and protocol modifications. In addition, HLA epitope-based analysis approaches to improve interpretation of antibody test results have been introduced. Summary: In the 50 years, since Patel and Terasaki first developed the crossmatch assay there have been remarkable advances in HLA antibody testing methodology. However, with these advances, new problems emerged and solutions had to be developed. As the technology continues to evolve, our methods and ability to interpret results must keep pace to provide transplant patients with the best possible care.