Test Overview
Test Usage

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.

Reference Range *

ADAMTS-13 Activity >67%. ADAMTS-13 Inhibitor <30%.

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Limitations

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.

Test Details
Days Set Up
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 .
Analytic Time

2 hours

Soft Order Code
MiChart Code
ADAMTS13 Activity
  • von Willebrand Factor Cleaving Protease
  • VWF Cleaving Protease
  • ADAMTS13 Inhibitor
  • ADAMTS13 Activity
STAT Availability

STAT availability and requests during non-business hours will require direct pathologist approval based on the patient's clinical presentation.

Specimen Requirements
Collection Instructions

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.

Normal Volume
Full 2.7 mL tube or 1 mL plasma aliquot
Minimum Volume
Full 1.8 mL tube or 1 mL plasma aliquot
Rejection Criteria
Samples collected in EDTA are not acceptable because EDTA is a strong inhibitor of ADAMTS13 function. Specimens will be rejected if not properly filled, clotted, grossly hemolyzed, or contaminated with heparin.
Additional Information

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.

CPT Code
Fee Code
Reflex CPT
Reflex Fee Code