ADAMTS13 and congenital thrombotic thrombocytopenic purpura: Deficiency or antibody against ADAMTS13 confirms the diagnosis of TTP and helps to discriminate thrombocytopenia, microangiopathic hemolytic anemia occurring independently from TTP.59,60 Although testing for ADAMTS13 is not routine in clinical laboratories, it is necessary to confirm TTP in the research setting.