Various methods have been proposed for the detection of HLA antibodies in organ transplantation. However, the discrepancies in the results between LCT (CDC)-XM and the other methods, FCXM, LABScreen etc. are observed. We investigated the cause of these discrepancies using the LABScreen Single Antigen Test (LABScreen) and LABScreen Single C1q (C1qScreen). C1qScreen is detected the complement-binding HLA antibody. As a result, in 37 patients whose HLA antibodies positive by using LABScreen test, 28 patients (76%) and 25 patients (68%) whose HLA Class I and Class II antibodies positive, respectively. Moreover, it was only 11 patients (30%) that C1qScreen was positive in the patients whose Class I antibodies were positive. And it was 14 patients (40%) that C1qScreen was positive in the patients whose Class II was positive. Furthermore C1qScreen positive was 176 (31%) among 567 specificity of detected Class I antibodies, and C1qScreen positive was 171 (44%) among 392 specificity of Class II. Therefore, many HLA antibodies are not detected by LCT-XM. It is because these antibodies do not have complement-binding nature. And such antibodies could be detected by AHG-LCT, and it is supposed that these are not related to kidney-allograft failure.