Abstract: The present invention provides a kit for the improved method for detection of panel-reactive antibodies in serum of a subject against HLA Class I antigens, which comprises an array of microbeads, each microbead presenting HLA antigens from a cell population presenting the same HLA antigens. In the method, serum from a subject is added to said array of microbeads then the mixture is incubated for a sufficient time for anti-HLA antibodies in the serum to bind to the HLA antigens presented on the microbeads. After removing serum components which do not specifically bind with the HLA antigens presented on said microbeads, the microbeads are incubated with a labeled ligand capable of specifically binding with anti-HLA antibodies bound to said HLA antigens. The labeled ligand which is not bound to said HLA antigens are removed and the presence of labeled ligand bound to said HLA antigens are detected by flow cytometry.