A 38-year-old man presented with episodes of severe headache. CNS imaging shows evidence of coical sinus venous thrombosis (CSVT). His mother has history of spontaneous recurrent DVT of bilateral lower limbs. Which of the following testing is the least likely to be indicated in this patient?

The patient is likely to have a hypercoagulable state, which is responsible for thrombosis at unusual site (coical venous sinus). There is positive family history of thrombosis also, indicating the underlying risk factor to be inherited. Hypercoagulable States: Primary (Genetic) Factor V Leiden mutation Prothrombin G20210A mutation (noncoding sequence variant leading to increased prothrombin levels) Increased levels of factors VIII, IX, XI, or fibrinogen (genetics unknown) Antithrombin III deficiency Protein C deficiency Protein S deficiency Fibrinolysis defects Homozygous homocystinuria (deficiency of cystathione b-synthetase) - increased homocysteine level Antiphospholipid antibodies are found in APLA syndrome which gives rise to secondary (acquired) hypercoagulable state.