ADAMTS13 Activity with Reflex to Inhibitor
Also known as: vWF-CP, vonWillebrand Factor, VWF Cleaving Protease, vWF Protease Activity
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
Specimen must be collected in a light‑blue (3.2 % sodium citrate) tube, centrifuged promptly (15 min at 1500 g within one hour), and plasma frozen immediately (separate vial per coagulation assay) and transported on dry ice. Reflex inhibitor testing incurs additional charge. Performing laboratory is Quest Diagnostics Nichols Institute, Chantilly, VA.
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.
Methodology
Immunoassay (ELISA)
Biomarkers
Result Turnaround Time
2-4 days
Related Documents
For more information, please review the documents below
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
Storage Instructions
Keep frozen
Causes for Rejection
Gross hemolysis, lipemia, icterus
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | Unacceptable |
| Refrigerated | Unacceptable |
| Frozen | 21 days |