Abstract Number: PB0058
Meeting: ISTH 2022 Congress
Background: Vaccine-induced immune thrombocytopenia (VITT) is a rare but serious complication of SARS-COV-2 vaccination and its diagnosis is based on both clinical and biological criteria.
Aims: To evaluate the performance of these criteria in a prospective cohort of patients with suspected VITT.
Methods: Among 105 consecutive patients (table 1), 79 had received one (n=71) or two (n=8) injections of adenoviral vector vaccine, and 26 one (n=18) or two (n=8) doses of an mRNA vaccine. Most patients presented thrombosis either isolated (n=40), or associated with thrombocytopenia (T+T=45). Other patients had isolated thrombocytopenia (n=15), or variable clinical manifestations. ELISA (PVS/PF4 HAT45G®) detected anti-PF4 antibodies, and when present VITT diagnosis was confirmed using PF4 serotonin release assay.
Results: VITT was confirmed in 26 patients (both PVS/PF4 ELISA and PF4/SRA were positive) and probable in one case (PVS/PF4 ELISA OD=2.4 but PF4/SRA negative). VITT was excluded in all patients who had received an mRNA vaccine, or in those with isolated thrombocytopenia or thrombosis or with other symptoms. In contrast, the presence of both thrombocytopenia and thrombosis 5 to 30 days after injection was highly suggestive of VITT with a specificity and PPV of 85% and 69%, respectively, these values increasing to 93.6% and 85% if patients had received adenoviral vector vaccine. Importantly, the PPV reached in these cases 100% when OD > 1 in ELISA. (Table)
Conclusion(s): Conclusion: The occurrence of thrombocytopenia and thromboses, 5 to 30 days after vaccination with an adenoviral vector is highly predictive of VITT. PF4/PVS ELISA allows to rule out VITT when OD is < 0.4 (NPV 100%) and to confirm the diagnosis when OD is > 1 without necessitating a platelet activation test. Moreover, the follow-up of patients with ELISA is mandatory since anti-PF4 antibodies may remain several weeks after VITT.
To cite this abstract in AMA style:Pouplard C, Vayne C, Guery E, Ajzenberg N, Cauchie P, Cordonnier C, De Maistre E, Donnard M, Drillaud N, Galinat H, Goffard S, Gouin I, Marlu R, Mourey G, Mullier F, SIGURET V, Susen S, Tuffigo M, Rollin J, Gruel Y. Contribution of biology to the diagnosis and follow-up of VITT: a French multicentre experience. [abstract]. https://abstracts.isth.org/abstract/contribution-of-biology-to-the-diagnosis-and-follow-up-of-vitt-a-french-multicentre-experience/. Accessed October 1, 2023.
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