Test Information

ADAMTS13 is a plasma protein that regulates the interaction of platelets with von Willebrand factor. Absent or low ADAMTS13 activity allows formation of platelet microthrombi, which in turn obstruct arterioles and capillaries, generating the clinical sequelae of Thrombotic thrombocytopenic purpura (TTP).

The majority of adults with idiopathic TTP have a severe deficiency of ADAMTS13 with activity levels <10%. The low levels are often due to autoantibodies that inhibit or clear ADAMTS13. Patients with idiopathic TTP usually require therapeutic plasma exchange to achieve clinical remission. Patients with idiopathic TTP and severe ADAMTS13 deficiency are more likely to respond to plasma exchange therapy than patients without severe deficiency. Persistence of ADAMTS13 deficiency or an inhibitor/antibody during clinical remission suggests an increased risk for recurrence of symptomatic TTP. Identification of an autoimmune mechanism in idiopathic TTP explains the rationale for immunotherapy.

Congenital severe ADAMTS13 deficiency is an autosomal recessive disorder (Upshaw-Schulman syndrome). Patients may present as children or adults, and are at risk for recurrent episodes of TTP. Antibody to ADAMTS13 is usually not detected, and patients generally improve with plasma transfusion therapy for ADAMTS13 replacement.