Background: Heparin-induced thrombocytopenia (HIT) antibodies develop in ~3% of patients with Heparin (H) administration. HIT is the most frequent immune-mediated adverse drug reaction involving blood cells and could be life-threatening. To detect HIT antibodies, immunological assays are widely used because of their high sensitivity (≥95%) and fast turnover, but only ~50% of these tests show a spectrum of clinical HIT. Pathogenic HIT antibodies can be better identified by functional assays such as the serotonin release assay or Heparin-induced platelet aggregation with an accuracy of over 90%. However, functional assays require fresh human blood and are only available in specialized laboratories/countries. Recently, we found that binding of Platelet Factor 4/Heparin (PF4/H) antibodies are qualitatively different.

Aims: We aim to develop an electrical sensor to better differentiate pathogenic antibodies from non-pathogenic antibodies based on their distinct binding characteristics.

Methods: As a model, we used monoclonal non-pathogenic antibody RTO and pathogenic antibody KKO. PF4/Heparin complexes were immobilized on gold chips and their binding was tracked in Quartz crystal microbalance (QCM) and Electrochemical impedance spectroscopy (EIS). Mass change (Sauerbry equation) and electron transfer rate (Nyquist fitting) were analyzed from QCM and EIS respectively. Binding strengths between antibodies and PF4/H complexes were determined by single-molecule force spectroscopy (SMFS).

Results: Mass change obtained by QCM and electron transfer rate detected by EIS increased when PF4/Heparin complexes were immobilized on the chips and further increased when KKO was added. No significant changes were observed when RTO was added. SMFS results consistently showed that KKO interacted with PF4/H complexes with stronger binding force than RTO.

Conclusions: Pathogenic HIT antibody KKO could be differentiated from the non-pathogenic antibody RTO. Our study provides a potential approach for better detection of pathogenic HIT antibodies from patients.

« Back to ISTH 2020 Congress

ISTH Congress Abstracts - https://abstracts.isth.org/abstract/detection-of-pathogenic-anti-platelet-factor-4-antibodies-by-impedance-spectroscopy/