Vaccine-Induced Thrombotic Thrombocytopenia: Novelty Testing in the Diagnostic Work-up?

COVID-19 vaccination campagnies with several vaccines types are currently undeway. Recently, the ASTRA ZENECA vaccine has raised public alarm with concerns regarding the development of thrombotic events known as vaccine-induced thrombotic thrombocytopenia (VITT). Early and limited studies have implicated an antibody-mediated platelet activation as the mechanism of the clotting events. Aim of this study was to investigate the platelet and coagulation activation using specialized tests. In this study we enrolled 60 patients (40 men, 20 women; mean age 55±10 years) without cardiovascular risk factors or a history of thrombosis who reported having poplitea deep vein thrombosis (35/60) and pulmonary embolism (25/60) revealed with lower-limb ultrasonography and computed tomography (CT) angiography, respectively, 7 days after vaccination with ASTRA ZENECA. All patients were evaluated for initial testing such as platelet count, prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen (Fib) and D-dimer (DD). Platelets were measured by automated analyzer, PT and APTT by coagulometric test, Fib using Clauss method, and DD using ELISA. Complete blood hemostasis was studied by platelet function assay (PFA-100) on Collagen/ADP (CT-ADP) and Collagen/Epinephrine (CT-EPI) cartridges and Thromboelastometry method on Clotting Time (CT), Clotting Formation Time (CFT), Maximum Clot Firmness (MCF), and clot lysis at 30 minutes (LY-30). All patients had thrombocytopenia (60±5x109/L), longer PT (28±10 s) and PTT (50±10 s), lower Fib (80±20 mg/dl), higher DD ((550±100 mg/l). All patients had shorter C/ADP and C/EPI (C/ADP, n.v. 68-121 s (42±10 s) and C/EPI n.v. 84-160 s (38±5 s) and shorter CT (CT, unit: s. n.v. 100-240 s) (INTEM 30±20 s, EXTEM 18±10 s), shorter CFT (CFT, unit: s, n.v. 30-160 s (INTEM 11±10 s, EXTEM 19±10 s), longer MCF (MCF, unit: mm, n.v. 50-72 mm (INTEM 128±10 mm, EXTEM 110±10 mm), and lower LY-30 (LY-30, %: v.n. 15% (INTEM 0.8%, EXTEM 0.7%). These interesting findings may be the novelty in the diagnostic work-up of the VITT. If these tests may aid in the diagnosis of VITT deserve to be confirmed and need reproducing in other studies.