ADAMTS13 Activity Testing: Evaluation of Two Automated Platforms for Diagnosis and Follow-Up of Thrombotic Thrombocytopenic Purpura.

Abstract

Introduction: Thrombotic thrombocytopenic purpura (TTP) is a rare but life-threatening thrombotic microangiopathy characterized by a severe deficiency of ADAMTS13 activity, typically defined as less than 10 IU/dL. Rapid and reliable measurement of ADAMTS13 activity is crucial for both timely diagnosis and effective long-term patient monitoring. While ELISA-based methods are widely used, automated assays offer potential advantages in terms of turnaround time and standardization. This study evaluates two automated ADAMTS13 activity assays, HemosIL AcuStar ADAMTS13 Activity Assay (Werfen) and TECHNOFLUOR ADAMTS13 Activity (Technoclone), in comparison to the TECHNOZYM ADAMTS13 Activity ELISA (Technoclone).

Methods: ADAMTS13 activity was measured in 100 patient samples using three assays: TECHNOZYM ADAMTS13 Activity ELISA, HemosIL AcuStar ADAMTS13 Activity, and TECHNOFLUOR ADAMTS13 Activity. Analytical performance and method comparison were assessed. Additionally, calibration against the WHO standard was evaluated.

Results: Both automated assays demonstrated high precision, with lower coefficients of variation (CV) compared to the ELISA. The HemosIL assay showed CVs ranging from 4.6% to 7.1%, while the TECHNOFLUOR assay exhibited CVs between 3.0% and 3.3%. ADAMTS13 activity measurements obtained with ELISA were significantly higher than those from both automated assays, which showed no statistically significant difference between them. Both automated assays achieved a sensitivity of 100%, with one false-positive TTP classification. The HemosIL assay showed the greatest bias between WHO and manufacturer-based calibrations.

Conclusion: The automated systems exhibit strong performance and rapid turnaround times, making them well-suited for routine ADAMTS13 determination. Standardization and calibration against international benchmarks, such as the WHO standard, is essential to minimize inter-assay variability and ensure reliable clinical interpretation.