Q. A 58 year-old man patient presents with right side of body weakness and speech abnormality. He is hospitalized for cerebrovascular accident (ischemic stroke) work-up and management. As part of routine DVT prophylaxis, the patient is started on heparin. During the admission, the patient develops chest pain. Work-up reveals a myocardial infarction. The patient's routine laboratory evaluation demonstrates elevated troponin level, PT and PTT are normal, platelet count is 35,000 per mcL (the patients' admission platelet count was 185,000 per mcL). The patient has no prior history of thrombocytopenia. You suspect heparin-induced thrombocytopenia (HIT) type II. In heparin-induced thrombocytopenia (HIT) type II, how long does it take for the platelet level to fall by at least 50% of the prior baseline?