PF4 and Venous thrombosis: A complete blood count, peripheral smear, D-dimer, fibrinogen, anti-PF4 heparin antibodies on the enzyme-linked immunosorbent assay (ELISA), and imaging (computed tomography or magnetic resonance imaging with venography or angiography) should be used to rule out thrombosis in individuals suspected of having TTS. In the absence of heparin treatment, anti-PF4 antibodies are highly indicative of TTS.