Detection of Platelet-Activating Antibodies Associated with Vaccine-Induced Thrombotic Thrombocytopenia by Flow Cytometry: An Italian Experience

• Published in: Viruses 2022-05, Vol.14 (6), p.1133
• Main Authors: Cesari, Francesca, Sorrentino, Silvia, Gori, Anna Maria, Rogolino, Angela, De Cristofaro, Raimondo, Giusti, Betti, Sticchi, Elena, De Candia, Erica, Marcucci, Rossella
• Format: Article
• Language: English
• Subjects: Analysis; Antibodies; Anticoagulants; Anticoagulants (Medicine); Blood platelets; Care and treatment; Communication; Coronaviruses; COVID-19; COVID-19 vaccines; Diagnosis; Dosage and administration; Enzyme-linked immunosorbent assay; Flow cytometry; Health care; Heparin; heparin-induced thrombocytopenia and thrombosis (HIT); HIPA; Hospitals; Immune response; Immunoassay; Immunoglobulins; Immunology; Intravenous administration; Laboratories; Monoclonal antibodies; mRNA; P-selectin; Pathogenicity; Patients; Plasma; Platelet activating factor; Platelets; Severe acute respiratory syndrome coronavirus 2; Thrombocytopenia; Thrombosis; vaccine-induced thrombocytopenia and thrombosis (VITT); Vaccines; Veins & arteries
• ISSN: 1999-4915; 1999-4915
• DOI: 10.3390/v14061133

Rare cases of thrombocytopenia and thrombosis after anti-COVID-19 adenovirus-associated mRNA vaccines (VITT) due to platelet-activating anti-platelet-factor 4 (PF4)/polyanion antibodies have been reported. VITT laboratory diagnosis, similarly to heparin-induced thrombocytopenia (HIT) diagnosis, requires immunoassays for anti-PF4/polyanion antibodies identification, such as ELISA assays and platelet-activating functional tests, such as heparin-induced platelet activation test (HIPA), to confirm their pathogenicity. We compared the flow cytometry (FC) measurement of platelet p-selectin exposure to the gold standard functional test HIPA for diagnosis confirmation in 13 patients with a clinical VITT syndrome (6M/7F; median age 56 (33–78)) who resulted positive to anti-PF4/polyanion antibodies ELISA assays (12/13). FC and HIPA similarly identified three different patterns: (1) a typical non-heparin-dependent VITT pattern (seven and six patients by FC and HIPA, respectively); (2) low/no platelet activation in patients under IvIg therapy (five out of five and two out of four patients by FC and HIPA, respectively); (3) a HIT pattern. Antibodies investigated by FC became negative after 7, 17, and 24 days of therapy in three patients. FC measurement of P-selectin exposure was as sensitive as HIPA but simpler to detect anti-PF4/polyanion antibodies in VITT patients. FC could reliably discriminate VITT from HIT, thus helping for the choice of the anticoagulant.