Lupus Anticoagulant
Also known as: LA, LAC
What Does Lupus Anticoagulant Measure?
Lupus anticoagulant (LA) is a blood test that detects abnormal antibodies — specifically antiphospholipid antibodies — that mistakenly attack phospholipid proteins on the surface of cells. Despite the name, these antibodies actually increase the risk of blood clotting (thrombosis) rather than causing bleeding, which is why they are considered 'anticoagulant' only in the laboratory setting where they interfere with clotting-based tests. The test is performed using a series of specialized clotting assays, typically including the dilute Russell's viper venom time (dRVVT) and the activated partial thromboplastin time (aPTT), to confirm the presence of these interfering antibodies.
Why Does Lupus Anticoagulant Matter?
Lupus anticoagulant is a critical marker for diagnosing antiphospholipid syndrome (APS), a serious autoimmune condition associated with an increased risk of arterial and venous blood clots, stroke, heart attack, pulmonary embolism, and recurrent pregnancy loss. It is also found in patients with systemic lupus erythematosus (SLE), though it can occur in people without lupus as well. Identifying a positive lupus anticoagulant result is crucial because it guides decisions about anticoagulation therapy, monitoring during pregnancy, and long-term management strategies to prevent life-threatening clotting events. Confirmatory testing is recommended after 12 weeks due to the possibility of transient positivity.
Normal Ranges
Males
Negative (not detected); ratio typically < 1.2 on confirmatory testing
Females
Negative (not detected); ratio typically < 1.2 on confirmatory testing
Children
Negative (not detected); same interpretation as adults
Causes of High Levels
- Antiphospholipid syndrome (APS) — the primary condition associated with persistent lupus anticoagulant positivity
- Systemic lupus erythematosus (SLE) — an autoimmune disease frequently linked to LA production
- Other autoimmune disorders such as rheumatoid arthritis or Sjögren's syndrome
- Certain infections including HIV, hepatitis C, and Lyme disease causing transient positivity
- Use of medications such as phenothiazines, hydralazine, procainamide, or certain antibiotics
- Malignancies including lymphoma and other hematologic cancers
Causes of Low Levels
- True negative result indicating absence of antiphospholipid antibodies
- Anticoagulation therapy (e.g., warfarin, heparin, direct oral anticoagulants) can interfere with testing and produce false-negative results
How to Improve Your Lupus Anticoagulant
Diet
- Follow an anti-inflammatory diet rich in omega-3 fatty acids from fatty fish, flaxseeds, and walnuts to support vascular health
- Increase intake of leafy green vegetables for antioxidant support, but maintain consistent vitamin K intake if on warfarin therapy
- Limit processed foods, trans fats, and excess saturated fats to reduce systemic inflammation and cardiovascular risk
- Stay well-hydrated to support healthy blood viscosity and reduce clotting risk
- Avoid excessive alcohol consumption, which can interact with anticoagulant medications and affect clotting factors
Supplements
- Omega-3 fatty acids (fish oil): 2–4 g/day EPA+DHA — discuss with physician as it may have mild antiplatelet effects
- Vitamin D: 1,000–2,000 IU/day to support immune regulation, particularly in autoimmune-related LA positivity (check levels first)
- Hydroxychloroquine (prescription): 200–400 mg/day — commonly prescribed for SLE-related APS to reduce thrombotic risk
- Avoid herbal supplements such as ginkgo biloba, garlic, and high-dose vitamin E without medical supervision, as they may increase bleeding risk in anticoagulated patients
Related Biomarkers
Frequently Asked Questions
What does it mean if I test positive for lupus anticoagulant?
A positive lupus anticoagulant result means that abnormal antibodies were detected in your blood that can increase your risk of blood clots. A single positive result does not confirm antiphospholipid syndrome — the test must be repeated and confirmed at least 12 weeks later to determine if the result is persistent. Your doctor will likely order additional tests, including anticardiolipin and anti-beta-2 glycoprotein I antibodies, to get a complete picture.
Can you have lupus anticoagulant without having lupus?
Yes, absolutely. Despite the name, lupus anticoagulant can occur in people who do not have lupus (SLE). It is found in individuals with antiphospholipid syndrome as a standalone condition (primary APS), as well as in people with other autoimmune diseases, certain infections, or even some medication exposures. The name is historical and refers to its discovery in lupus patients, not an exclusive association.
Does lupus anticoagulant cause bleeding or clotting?
Counterintuitively, lupus anticoagulant causes clotting in the body, not bleeding. The term 'anticoagulant' only refers to its behavior in laboratory test tubes, where it interferes with phospholipid-dependent clotting assays and artificially prolongs clotting times. In real blood vessels, these antibodies promote the formation of dangerous blood clots in both arteries and veins.
How is lupus anticoagulant diagnosed?
Diagnosis requires a two-step laboratory process: first, a screening test (such as dRVVT or aPTT) shows prolonged clotting time; second, a mixing study confirms the prolongation is not due to a clotting factor deficiency but is caused by an inhibitor. Finally, a phospholipid confirmation step proves the inhibitor is phospholipid-dependent. All three criteria must be met, and results must be confirmed on a repeat test at least 12 weeks later.