- This unfortunate patient case highlights the problems with "overdiagnosis" of HIT. Despite "positive" tests for HIT antibodies, the low pretest probability for HIT and the known propensity of patients with APS to yield false-positive HIT antibody results suggests that the patient did not have a true diagnosis of HIT. Moreover, the early administration of warfarin and the choice of argatroban for parenteral anticoagulation when monitoring was hindered by a prolonged baseline aPTT likely play a key factor in the progression of UE DVT to VLG. Ironically, the problems of anticoagulant monitoring posed by the prolonged baseline aPTT likely contributed to the subsequent overanticoagulation and fatal pulmonary hemorrhage. With benefit of hindsight, avoiding the temptation to test for HIT in a low pretest probability situation, and treatment with either heparin using anti-factor Xa monitoring or with non-aPTT-monitored therapy such as LMWH or fondaparinux would likely have resulted in a more favorable clinical course.