ADAMTS13 Activity with Reflex to Inhibitor

Also known as: vWF-CP, vonWillebrand Factor, VWF Cleaving Protease, vWF Protease Activity

Clinical Use

Use

ADAMTS‑13 is a zinc metalloprotease responsible for cleaving ultra‑large von Willebrand factor multimers. Reduced ADAMTS‑13 activity is associated with thrombotic thrombocytopenic purpura (TTP), a life‑threatening hematologic condition marked by thrombocytopenia, microvascular thrombi, hemolytic anemia, and potential renal impairment. Congenital TTP arises from mutations in the ADAMTS‑13 gene producing nonfunctional enzyme, while the acquired form stems from autoantibodies that inhibit ADAMTS‑13 activity. Reflex testing for ADAMTS‑13 inhibitor is triggered when activity is ≤0.30 IU/mL. Results are reported in IU/mL (activity) and Bethesda equivalent units for inhibitor. This test aids in differentiating congenital vs acquired TTP and informing therapeutic decisions.

Special Instructions

Not provided.

Limitations

Interference may occur with bilirubin >20 mg/dL or hemolysis >1500 mg/dL. Plasma exchange may alter results by elevating activity and lowering inhibitor level. Antibody presence does not necessarily reflect inhibitory activity, as non‑pathologic antibodies may be detected in healthy individuals or those with systemic lupus erythematosus.

Test Details

Methodology

Immunoassay (ELISA)

Biomarkers

2 components

ADAMTS13 Activity • ELISAADAMTS13 Inhibitor (reflex) • ELISA

Result Turnaround Time

2-4 days

Specimen

Plasma

Volume

1 mL (preferred), minimum 0.5 mL

Minimum Volume

0.5 mL

Container

Light‑blue top tube (3.2 % sodium citrate); separate plastic vial for frozen plasma

Collection Instructions

Draw blood in light‑blue tube, invert gently 3‑4 times; centrifuge 15 min at 1500 g within 1 hour; remove plasma avoiding buffy layer; freeze immediately; separate vial per coagulation assay