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. The gene discussed is ADAMTS13; the disease is Thrombocytopenia.