ADAMTS13 and thrombotic thrombocytopenic purpura: The described approach might also include congenital TTP cases as anti-ADAMTS13 antibodies measurement was only available in 69% of patients (n = 60 of n = 87 cases); hence a differentiation between congenital TTP and acquired TTP, on the basis of the absence of anti-ADAMTS13 antibodies, was not possible in all patients.