Abstract Number: OC 02.3
Meeting: ISTH 2022 Congress
Theme: Platelet Disorders, von Willebrand Disease and Thrombotic Microangiopathies » HIT
Background: Heparin-induced thrombocytopenia (HIT) and vaccine-induced immune thrombotic thrombocytopenia (VITT) are life-threatening disorders characterized by anti-Platelet Factor 4 (PF4) antibodies. Tests such as the PF4-polyanion enzyme-linked immunosorbent assay (ELISA) lack specificity, and accurate functional tests such as the serotonin release assay (SRA) and PF4-dependent P-selectin expression assay (PEA) are technically complex and require fresh platelets; causing delays in diagnosis and overuse of alternative anticoagulants.
Aims: Develop a rapid, near-patient assay for diagnosing HIT and VITT using readily available “off-the-shelf” platelets.
Methods: Normal donor platelets were cryopreserved in a trehalose-based buffer. Thawed platelets were washed, treated with PF4 or heparin, and incubated with HIT or VITT samples before quantifying platelet thrombospondin-1 (TSP1) release in the TSP1-release assay (TRA). Results were expressed relative to TSP1 released by healthy donor serum-treated cryopreserved platelets.
Results: Platelet-activating (PEA-positive) samples stimulated a 2.52-fold mean increase in TSP1 release in the PF4-TRA (Fig 1A), and an average 2.79-fold increase in the heparin-TRA (Fig 1B), both significantly higher than TSP1 release induced by PEA-negative HIT-suspected patients (including some with false-positive ELISA results; red squares). Two non-activating samples induced TSP1 release in the heparin-TRA but were not inhibited by high-dose heparin (100 U/mL; data not shown), ruling out HIT. Cryopreserved platelets stored for >1 year supported detection of HIT antibodies (data not shown). Lastly, four VITT patient samples induced elevated TSP-1 release in the PF4-TRA (Fig 1A) but did not in the Heparin-TRA (Fig 1B).
Conclusion(s): The PF4- and Heparin-TRA were highly accurate for diagnosing HIT/VITT and HIT, respectively. VITT samples did not activate heparin-treated platelets, likely due to competition for the heparin-binding site on PF4. The use of “off-the-shelf” cryopreserved platelets has the potential to transform the diagnostic testing paradigm by making near-patient functional testing available for the rapid and accurate diagnosis of HIT and VITT.
To cite this abstract in AMA style:
Kanack A, Jones C, Splinter N, Leger R, Heikal N, Chen D, Pruthi R, George G, Abou-Ismail Y, Wool G, Gundabolu K, Padmanabhan A. “Off-the-shelf” cryopreserved platelets for the detection of HIT and VITT antibodies [abstract]. https://abstracts.isth.org/abstract/off-the-shelf-cryopreserved-platelets-for-the-detection-of-hit-and-vitt-antibodies/. Accessed August 9, 2022.« Back to ISTH 2022 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/off-the-shelf-cryopreserved-platelets-for-the-detection-of-hit-and-vitt-antibodies/