Factor XII Inhibitor (Antithrombin Activity) – Plasma
This test measures the presence of antibodies that may block the natural blood-clotting process by inhibiting Factor XII, a protein involved in clotting and inflammation pathways. It is often used to diagnose or monitor conditions related to abnormal bleeding or clotting disorders.
["This test helps assess bleeding risks linked to rare clotting disorders caused by Factor XII deficiency or inhibitor presence."]
Key facts at a glance
- LOINC
- 3230-0
- Short code
- Fact XII Inhib PPP-aCnc
- Synonyms
- Fact XII Inhib PPP-aCnc
- Category
- chemistry
- Sample
- plasma
- Container
- Lavender-top (EDTA) or Green-top (Heparin)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- coag
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why This Test Might Be Ordered
Your healthcare provider may recommend this test if you have unexplained bleeding, prolonged bleeding after injuries or surgeries, or if you have a family history of bleeding disorders. It may also be used in patients suspected of having rare clotting or inflammatory conditions linked to Factor XII.
What to Expect Before the Test
No special preparation is needed. You may have a blood draw from a vein in your arm. If you’re on anticoagulant medications, inform your provider before the test.
What the Test Results Mean
Results are qualitative (positive or negative) and indicate whether Factor XII inhibitor antibodies are present. A positive result suggests a potential bleeding disorder requiring further evaluation.
Common Conditions Monitored
This test helps diagnose or monitor conditions like acquired Factor XII inhibitor syndrome, which can cause bleeding in people with otherwise normal clotting systems.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical significance: Factor XII inhibitors can interfere with normal blood clotting and inflammation processes, potentially leading to excessive bleeding in certain situations. It is particularly relevant for patients with unexplained bleeding or those undergoing procedures requiring precise coagulation control.
Short name
Factor XII Inhibitor
Frequently asked questions
What causes Factor XII inhibitors to develop?
How is this test different from standard clotting tests like PT/PTT?
Can lifestyle changes affect Factor XII inhibitor test results?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy