Platelet-activating functional assay resolution in vaccine-induced immune thrombotic thrombocytopenia: differential alignment to PF4 ELISA platforms

Anti-platelet factor 4 (PF4) antibodies in vaccine-induced immune thrombotic thrombocytopenia (VITT) appear to be transient, with discrepant persistence depending on the platform used for detection. We aimed to report a longitudinal study of antibody persistence using 2 ELISA platforms and 2 platele...

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Bibliographic Details
Published in:	Research and practice in thrombosis and haemostasis Vol. 7; no. 3; p. 100128
Main Authors:	Lee, Christine S.M., Clarke, Lisa J., Kershaw, Geoffrey W., Tohidi-Esfahani, Ibrahim, Brighton, Timothy A., Chunilal, Sanjeev, Favaloro, Emmanuel J., Tran, Huyen, Chen, Vivien M.
Format:	Journal Article
Language:	English
Published:	United States Elsevier Inc 01-03-2023 Elsevier
Subjects:	Brief Report COVID -19 vaccine enzyme-linked immunosorbent assay platelet activation platelet factor 4 vaccine-induced immune thrombotic thrombocytopenia vaccine-induced immune thrombotic thrombocytopenia COVID -19 vaccine platelet factor 4 platelet activation enzyme-linked immunosorbent assay
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Summary:	Anti-platelet factor 4 (PF4) antibodies in vaccine-induced immune thrombotic thrombocytopenia (VITT) appear to be transient, with discrepant persistence depending on the platform used for detection. We aimed to report a longitudinal study of antibody persistence using 2 ELISA platforms and 2 platelet-activating functional assays in a clinical cohort of patients with VITT referred for follow-up testing. In total, 32 Australian patients with VITT or pre-VITT, confirmed by expert adjudication, with samples referred for clinical follow-up were included. Clinical follow-up assays, including Stago and Hyphen ELISAs, procoagulant platelet flow cytometry, and modified PF4-serotonin-release assay, were performed according to the pattern of reactivity for that patient at diagnosis. The median follow-up was 24 weeks after diagnosis. A general decline in anti-PF4 antibody levels and platelet-activating capacity over time was observed with a more rapid median time to resolution of 16 weeks by functional assay vs 24 weeks by Stago ELISA. Decline in platelet-activating antibody levels detected by functional assays mirrored Stago ELISA titer but not Hyphen. However, 87% of patients received a documented second vaccination and 74% received an mRNA booster with no reported adverse events. Anti-PF4 antibodies persist longer than functional platelet-activating antibodies in VITT but do not warrant avoidance of subsequent vaccinations. Persistence detection is assay-dependent. Stago ELISA may be a surrogate where functional assays are unavailable for follow-up testing of confirmed patients with VITT. •Antibodies in vaccine-induced immune thrombotic thrombocytopenia (VITT) decline over time.•Serial testing of patients with VITT is advised to guide treatment duration.•Platelet-activating antibodies resolved earlier than those detected by Stago or Hyphen ELISAs.•No adverse events were reported following subsequent vaccinations of patients after VITT diagnosis.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	2475-0379 2475-0379
DOI:	10.1016/j.rpth.2023.100128