This test should be regarded as 'Research Use Only'. The performance characteristics were determined by Marshfield Labs in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration. It may not be covered by insurance and providers need to inform all patients of this prior to ordering.
For Medicare patients, an Advanced Beneficiary notice (ABN) is required; for Medicaid patients, a Noncovered Services Waiver is required, and for commercial payers, prior authorization should be obtained.
ADAMTS13 Activity is always performed. If activity is below the stated reference range, the inhibitor may be performed following internal pathologist review. ADAMTS13 is a plasma protein that regulates the size of the 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). ADAMTS13 deficiency can be congenital or acquired. In idiopathic TTP, acquired deficiency of ADAMTS13 is attributed to the presence of autoantibody, which may either inhibit ADAMTS13 function (which is reported as an inhibitor) or may cause clearance of circulation ADAMTS13. While patients with congenital deficiency of ADAMTS13 respond to simple plasma infusion therapy, patients with idiopathic TTP usually require therapeutic plasma exchange to achieve clinical remission.
The rapid ADAMTS13 test (Testcode ADAMT13) is recommended when the diagnosis of thrombotic thrombocytopenia purpura (TTP) is being considered and therapeutic decisions hang in the balance (e.g. placement of a central line and initiation of plasma exchange). Same day turn-around-time (TAT) is necessary and the rapid ADAMTS13 in-house assay performed by Marshfield Laboratories is appropriate.
For follow-up of a patient with TTP to assess recurrence risk, a more delayed TAT is acceptable, and the less expensive sendout ADAMTS13 test (Testcode ADAMTSO) is appropriate.
Consultation with a hematologist, hematopathologist, or coagulation specialist is advised for unusual clinical situations.