ADAMTS13 and thrombotic thrombocytopenic purpura: Microangiopathies such as thrombotic thrombocytopenic purpura, caused by ADAMTS13 deficiency, leading to microangiopathic hemolytic anemia and thrombocytopenia with neurological symptoms, renal impairment, and schistocytes on a blood smear, can be ruled out using the ADAMTS13 activity assay.