Fig. 1.

Diagnostic flow chart of VITT based on International Society on Thrombosis and Haemostasis Interim Guidance (updated 20 April 2021). In Korea, the PF4 ELISA is currently performed by sending a sample after reporting a suspected patient case to the Korea Disease Control and Prevention Agency. COVID, coronavirus disease; PT, prothrombin time; aPTT, activated partial thromboplastin time; PF4, platelet factor 4; ELISA, enzyme-linked immunosorbent assay; VITT, vaccine-induced immune thrombotic thrombocytopenia.