A novel automated chemiluminescent enzyme immunoassay (CLEIA) for ADAMTS13 activity enables accompanying measurements of the inhibitory autoantibodies

Thrombotic thrombocytopenic purpura (TTP) is a fatal disease caused by severe deficiency in ADAMTS13 activity. ADAMTS13 activity measurement is essential for the diagnosis of TTP, but conventional standard assays are manual and time-consuming. Automated ADAMTS13 activity assays have recently become available; however, their accuracy remains challenging. We here developed a novel chemiluminescent enzyme immunoassay (CLEIA) for ADAMTS13 activity that is fully automated, highly sensitive, and has a short reaction time (17 min). We evaluated the utility of our fully automated CLEIA for measuring ADAMTS13 activity and inhibitory antibodies and compared it with conventional manual assays. We compared our CLEIA for ADAMTS13 activity and inhibitory antibodies with an in-house FRETS-VWF73 assay and commercial enzyme-linked immunosorbent assay (ELISA) using samples from 100 patients and 50 healthy donors. Agreement between assays was evaluated using a cutoff value of 10 IU/dl for ADAMTS13 activity and 0.5 BU/ml for inhibitory antibodies. The CLEIA and conventional assays for ADAMTS13 activity correlated well. The CLEIA showed high agreement with the FRETS-VWF73 assay (kappa = 0.96) and ELISA (kappa = 1.0) in classifying patients with a cutoff value of 10 IU/dl for ADAMTS13 activity. Furthermore, in classifying patients with the cutoff value of 0.5 BU/ml for inhibitory antibodies, the CLEIA agreed strongly with the FRETS-VWF73 assay (kappa = 0.95) and ELISA (kappa = 0.98). Its diagnostic performance for TTP was satisfactory. The high-performance and fully automated CLEIA enables rapid in-hospital diagnosis and follow-up of TTP, as well as detection of inhibitory ADAMTS13 autoantibodies.