Diagnosis of thrombotic thrombocytopenic purpura: easy-to-use fiber optic surface plasmon resonance immunoassays for automated ADAMTS-13 antigen and conformation evaluation

J Thromb Haemost. 2024 Jul;22(7):1936-1946. doi: 10.1016/j.jtha.2024.03.012. Epub 2024 Mar 28.

Abstract

Background: Laboratory diagnosis of immune-mediated thrombotic thrombocytopenic purpura (iTTP) remains challenging when ADAMTS-13 activity ranges between 10% and 20%. To prevent misdiagnosis, open ADAMTS-13 conformation gained clinical attention as a novel biomarker, especially to diagnose acute iTTP in patients with diagnostic undecisive ADAMTS-13 activity. Plasma ADAMTS-13 conformation analysis corrects for ADAMTS-13 antigen, with both parameters being characterized in enzyme-linked immunosorbent assay (ELISA)-based reference assays requiring expert technicians.

Objectives: To design ADAMTS-13 antigen and conformation assays on automated, easy-to-use fiber optic surface plasmon resonance (FO-SPR) technology to promote assay accessibility and diagnose challenging iTTP patients.

Methods: ADAMTS-13 antigen and conformation assays were designed on FO-SPR technology. Plasma of 20 healthy donors and 20 acute iTTP patients were quantified, and data from FO-SPR and ELISA reference assays were compared.

Results: Following assay design, both antigen and conformation FO-SPR assays were optimized and characterized, presenting strong analytical sensitivity (detection limit of 0.001 μg/mL) and repeatability (interassay variation of 14.4%). Comparative analysis suggested positive correlation (Spearman r of 0.92) and good agreement between FO-SPR and ELISA assays. As expected, FO-SPR assays showed a closed or open ADAMTS-13 conformation in healthy donors and acute iTTP patients, respectively.

Conclusion: Both ADAMTS-13 antigen and conformation assays were transferred onto automated, easy-to-use FO-SPR technology, displaying potent analytical sensitivity and reproducibility. ADAMTS-13 antigen and conformation were determined for healthy donors and acute iTTP patients showing strong correlation with ELISA reference. Introducing FO-SPR technology in clinical context could support routine diagnosis of acute iTTP patients, notably when ADAMTS-13 activity fluctuates between 10% and 20%.

Keywords: ADAMTS-13 protein; enzyme immunoassay; laboratory diagnosis; purpura; surface plasmon resonance; thrombotic thrombocytopenic.

MeSH terms

  • ADAMTS13 Protein* / blood
  • ADAMTS13 Protein* / immunology
  • Automation, Laboratory
  • Biomarkers / blood
  • Case-Control Studies
  • Enzyme-Linked Immunosorbent Assay* / methods
  • Female
  • Humans
  • Immunoassay / methods
  • Male
  • Predictive Value of Tests
  • Protein Conformation
  • Purpura, Thrombotic Thrombocytopenic* / blood
  • Purpura, Thrombotic Thrombocytopenic* / diagnosis
  • Purpura, Thrombotic Thrombocytopenic* / immunology
  • Reproducibility of Results
  • Surface Plasmon Resonance*

Substances

  • ADAMTS13 Protein
  • ADAMTS13 protein, human
  • Biomarkers