[Introduction]At our institution, we perform HLA single antigen tests in addition to CDC and FCXM as tests before kidney transplantation. By performing these tests in combination, it is possible to ascertain the specificity and strength of anti-HLA antibodies in more detail. We report a case of chronic active antibody mediated rejection (CAAMR) in which the relevant HLA Eplet was detected by Eplet analysis after a LABScreen single antigen test. [Case]71-year-old male with DM nephropathy. The immunological test at the first visit was CDC negative, FCXM negative, and HLA SA confirmed NDSA. In 2022, he underwent a ABO incompatible kidney transplantation from type B to O. [Course after transplantation]Chronic antibody-related rejection was observed in routine biopsy 3 months after transplantation. However, no DSA was observed in HLA SA. Eplet analysis detected associated HLA eplets. This related HLA Eplet also contained mismatched antigens, suggesting the possibility that the antibody within this related HLA Eplet affected this reaction. [summary]Through this case, I reaffirmed the need to use CREG and Eplet analyzes well and carefully when determining antibody specificity.