A comparative study of anti-ADAMTS-13 antibody dynamics in immune-mediated thrombotic thrombocytopenic purpura

Maria Rita Cozzi; Fabio Del Ben; Chiara Corso; Agostino Steffan

doi:10.1016/j.rpth.2024.102525

A comparative study of anti-ADAMTS-13 antibody dynamics in immune-mediated thrombotic thrombocytopenic purpura

Res Pract Thromb Haemost. 2024 Jul 22;8(5):102525. doi: 10.1016/j.rpth.2024.102525. eCollection 2024 Jul.

Authors

Maria Rita Cozzi¹, Fabio Del Ben¹, Chiara Corso¹, Agostino Steffan¹

Affiliation

¹ Centro di Riferimento Oncologico (CRO) Aviano, National Cancer Institute, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Immunopathology and Cancer Biomarkers Unit, Department of Cancer Research and Advanced Diagnostics, Aviano, Italy.

Abstract

Background: Thrombotic thrombocytopenic purpura, particularly its immune-mediated variant (iTTP), necessitates accurate diagnostic approaches for effective management.

Objectives: To compare a chemiluminescence immunoassay (CLIA) and an enzyme-linked immunosorbent assay (ELISA) for testing ADAMTS-13 activity and detecting anti-ADAMTS-13 autoantibodies (AAbs) in patients with iTTP.

Methods: This study involved 31 paired samples from 12 iTTP patients. ADAMTS-13 activity was measured using the HemosIL AcuStar (Instrumentation Laboratory, CLIA) and Technozym (Technoclone) activity assay (ELISA). The presence of AAbs was assessed using Technozym ADAMTS-13-INH assay (ELISA) and HemosIL AcuStar activity (CLIA) within a Bethesda assay following mixing with normal pool plasma. von Willebrand factor (VWF) multimers were analyzed using the HYDRASYS-2 SCAN system and the HYDRAGEL 5- or 11-VW Multimer kits (Sebia). VWF activity levels were measured with the HemosIL AcuStar VWF:GPIbR on the ACL AcuStar Analyzer (IL).

Results: For ADAMTS-13 activity, a strong linear relationship and no bias between CLIA and ELISA were confirmed (slope = 1.01 [0.91, 1.11], intercept = 0.00 [-0.47, 0]). However, significant discrepancies were found in AAb detection during remission phases with ADAMTS-13 activity between 10% and 50%, with CLIA and ELISA showing significant divergence (P < .001, Cohen's g = 0.34). Consistently, VWF multimers and activity levels exhibited significantly different values between remission samples with ADAMTS-13 activity below 50% and above 50%. In longitudinal analysis of patients with multiple iTTP relapses, positivity to CLIA appears to precede ELISA in predicting exacerbations.

Conclusion: While CLIA and ELISA might be interchangeable for assessing ADAMTS-13 activity, they are not equivalent for detecting AAbs, particularly in patients in clinical remission with ADAMTS-13 activity between 10% and 50%.

Keywords: ADAMTS-13; acquired ADAMTS13 protein; anti–ADAMTS-13 autoantibodies; enzyme-linked immunosorbent assay; immune-mediated thrombotic thrombocytopenic purpura; luminescent measurements; purpura; thrombotic thrombocytopenic; thrombotic thrombocytopenic purpura; von Willebrand factor.