In vitro studies have also shown that bivalirudin prolongs the activated partial thromboplastin time (aPTT) thrombin time (TT) and pro-thrombin time (PT) of normal human plasma in a concentration- dependent manner and that bivalirudin does not induce a platelet aggregation response against sera from patients with a history of Heparin-Induced Thrombocytopenia/ Thrombosis Syndrome (HIT/ HITTS).