Detection of Platelet-Activating Antibodies Associated with Vaccine-Induced Thrombotic Thrombocytopenia by Flow Cytometry: An Italian Experience
Francesca Cesari,
Silvia Sorrentino,
Anna Maria Gori,
Angela Rogolino,
Raimondo De Cristofaro,
Betti Giusti,
Elena Sticchi,
Erica De Candia,
Rossella Marcucci
Affiliations
Francesca Cesari
Atherothrombotic Disease Unit, Department of Experimental and Clinical Medicine, University of Florence, Azienda Ospedaliera Universitaria Careggi, 50141 Florence, Italy
Atherothrombotic Disease Unit, Department of Experimental and Clinical Medicine, University of Florence, Azienda Ospedaliera Universitaria Careggi, 50141 Florence, Italy
Angela Rogolino
Atherothrombotic Disease Unit, Department of Experimental and Clinical Medicine, University of Florence, Azienda Ospedaliera Universitaria Careggi, 50141 Florence, Italy
Atherothrombotic Disease Unit, Department of Experimental and Clinical Medicine, University of Florence, Azienda Ospedaliera Universitaria Careggi, 50141 Florence, Italy
Elena Sticchi
Atherothrombotic Disease Unit, Department of Experimental and Clinical Medicine, University of Florence, Azienda Ospedaliera Universitaria Careggi, 50141 Florence, Italy
Atherothrombotic Disease Unit, Department of Experimental and Clinical Medicine, University of Florence, Azienda Ospedaliera Universitaria Careggi, 50141 Florence, Italy
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.
