Severe deficiency of ADAMTS-13 (activity <5-10%) may be acquired or congenital, and is a relatively specific finding in patients with a clinical diagnosis of thrombotic thrombocytopenic purpura (TTP). TTP is a rare and potentially fatal thrombotic microangiopathy syndrome, characterized by symptoms such as thrombocytopenia, microangiopathic hemolytic anemia (intravascular hemolysis with presence of schistocytes), neurological symptoms, fever, and renal dysfunction. In this patient population, persistence of severe ADAMTS-13 deficiency during clinical remission is associated with an increased risk for recurrent clinical episodes of TTP. Mild to moderate deficiency of ADAMTS-13 activity has also been observed in multiple medical conditions.
ADAMTS-13 Activity >67%. ADAMTS-13 Inhibitor <30%.
Recent plasma exchange or transfusion may falsely normalize ADAMTS13 levels, thus potentially masking the diagnosis of TTP. Mild to moderate deficiency of ADAMTS13 activity has been observed in multiple medical conditions. Levels are generally normal in patients with marrow transplant-associated thrombotic microangiopathy and childhood hemolytic uremic syndrome. Interferences of ADAMTS13 activity assay include high levels of endogenous von Willebrand factor, hyperlipidemia, hemolysis with plasma free hemoglobin >2 g/L (>200mg/dl), hyperbilirubinemia (bilirubin concentration >5.8 mg/dl)and cleavage by other protease.
Monday - Friday, 8am - 4pm one run per day.
Specimen must be received by noon or will be tested the next business day.
Testing will not be performed on holidays or weekends .
- von Willebrand Factor Cleaving Protease
- VWF Cleaving Protease
- ADAMTS13 Inhibitor
- ADAMTS13 Activity
STAT availability and requests during non-business hours will require direct pathologist approval based on the patient's clinical presentation.
Collect specimen in a blue top (citrate 3.2%) tube. Mix by inversion. Specimen should arrive at lab within 3 hours of collection; transport at room temperature. Alternatively, centrifuge, aliquot plasma into a polypropylene plastic vial, and freeze the specimen within 4 hours of collection. Transport frozen specimen on dry ice. Collection of the blood through lines that have been previously flushed with heparin should be avoided. If the blood must be drawn through a VAD (vascular access device), the line should be flushed with 5 mL of saline and the first 5 mL of blood or six dead space volumes of the VAD discarded.
If Activity result is <30%, Inhibitior assay will be performed at an additional charge. By ordering this test the clinician acknowledges that additional reflex testing will be performed and billed at a separate additional charge if indicated.