Abstract

Background: Coronavirus disease 2019 (COVID-19) vaccines may cause rare hematological complications such as vaccine-induced immune thrombotic thrombocytopenia (VITT). In this study, we aim to present our experience and share insights into the diagnostic work-up for patients with a high probability
of VITT and assess the utility of the 4Ts score in VITT diagnosis.

Patients and methods: The study investigated VITT risks in patients from July to December 2021. Symptomatic individuals post-COVID-19 vaccination were enrolled and underwent anti-PF4 antibody testing, platelet counts, D-dimer tests, and imaging studies. Positive cases underwent heparin-induced platelet
aggregation tests for VITT confirmation. The 4Ts scoring system, adapted for VITT, incorporated anti-PF4 antibody titers, aiding in assessing probability based on specific titer ranges.

Results: Between July and December 2021, 18 patients with suspected VITT were studied. The median age was 55, with 66.7% men. Symptoms emerged  within amedian of 13 days post-vaccination. Vaccine brands varied, with 66.7% receiving ChAdOx1. Deep vein thrombosis occurred in 44.4%, and 11.1% had
autoimmune diseases. The median anti-PF4 level was 65.3 ng/mL. Treatment modalities included anticoagulants (50%), steroids (66.7%), and intravenous immunoglobulin (16.7%). One confirmed VITT case presented with ischemic bowel disease, a platelet count of 11000/μL, a 4Ts score of 7, and received plasma exchange. Retrospective application of the modified 4Ts scores classified patients into low, intermediate, and high probability groups.

Conclusion: The study highlights VITT's clinical features and diagnostic challenges, advocating for 4Ts score use in identifying high-risk cases. Larger studies are warranted to validate these findings.