A novel automated chemiluminescent enzyme immunoassay for ADAMTS-13 activity enables accompanying measurements of the inhibitory autoantibodies.

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is a fatal disease caused by severe deficiency in ADAMTS-13 (a disintegrin and metalloproteinase with thrombospondin type 1 motifs 13) activity. ADAMTS-13 activity measurement is essential for the diagnosis of TTP, but conventional standard assays are manual and time-consuming. Automated ADAMTS-13 activity assays have recently become available; however, their accuracy remains challenging.

OBJECTIVES

We here developed a novel chemiluminescent enzyme immunoassay (CLEIA) for ADAMTS-13 activity that is fully automated, highly sensitive, and has a short reaction time (17 minutes). We evaluated the utility of our fully automated CLEIA for measuring ADAMTS-13 activity and inhibitory antibodies and compared it with conventional manual assays.

METHODS

We compared our CLEIA for ADAMTS-13 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 international units/dL for ADAMTS-13 activity and 0.5 Bethesda units/mL for inhibitory antibodies.

RESULTS

The CLEIA and conventional assays for ADAMTS-13 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 international units/dL for ADAMTS-13 activity. Furthermore, in classifying patients with the cutoff value of 0.5 Bethesda units/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.

CONCLUSION

The high-performance and fully automated CLEIA enables rapid in-hospital diagnosis and follow-up of TTP, as well as detection of inhibitory ADAMTS-13 autoantibodies.