The Misleadingly Named Clotting Antibody
The name is doubly misleading: it's not specific to lupus, and it's not an anticoagulant. Lupus anticoagulant is an antibody that prolongs clotting tests in the lab (looks like it's an anticoagulant) but actually PROMOTES clotting in the body. It's part of antiphospholipid syndrome—a condition that causes blood clots and pregnancy complications.
What is Lupus Anticoagulant?
Lupus anticoagulant (LA) is an antiphospholipid antibody that interferes with phospholipid-dependent clotting tests (prolonging aPTT) but is prothrombotic in vivo. Part of antiphospholipid syndrome (APS). Diagnosed by DRVVT and/or aPTT-LA with mixing and confirm steps.
↑ What High Lupus Anticoagulant Means
Positive lupus anticoagulant is a significant finding—it indicates antiphospholipid antibodies that increase the risk of blood clots (DVT, PE, stroke) and pregnancy complications (recurrent miscarriage, preeclampsia). Must be confirmed positive on two occasions 12 weeks apart.
Common symptoms:
DVT, PE, or stroke (thrombotic APS) · Recurrent miscarriage (obstetric APS) · Livedo reticularis (mottled skin) · Thrombocytopenia · Catastrophic APS: multi-organ failure (rare)
↓ What Low Lupus Anticoagulant Means
N/A—this is a positive/negative test.
Common symptoms:
No symptoms—negative test
Why It Matters
When normal:
Identifies antiphospholipid syndrome
Explains unexplained clots, especially arterial
Explains recurrent pregnancy loss
Guides long-term anticoagulation decisions
Risks if abnormal:
Positive LA: significant risk of venous AND arterial thrombosis
Recurrent pregnancy loss, preeclampsia
APS can cause catastrophic multi-organ failure (rare)
What Can Cause Abnormal Levels?
Antiphospholipid Syndrome
50% likelyAutoimmune condition with persistent antiphospholipid antibodies plus thrombosis or pregnancy morbidity.
Transient (post-infection)
35% likelyInfections can trigger temporary LA that resolves. Must confirm persistence at 12 weeks.
Lupus (SLE)
APS occurs in ~30-40% of lupus patients (secondary APS).
Other Autoimmune Disease
Can be associated with various autoimmune conditions.
Medications
Phenothiazines, hydralazine, and others can induce LA.
What You Can Do
Confirm positive result at 12 weeks (transient LA is common and not clinically significant)
Impact: Distinguishes persistent (clinically relevant) from transient \u00B7 Timeline: 12 weeks
Cannot test on anticoagulation (interferes with assay)
Impact: Test before starting or during bridging \u00B7 Timeline: As needed
If lifestyle changes aren't enough:
If confirmed APS: lifelong awareness of clot risk
Impact: Avoid additional risk factors: smoking, OCP, immobility \u00B7 Timeline: Lifelong
Low-dose aspirin for obstetric APS
Impact: Plus heparin in pregnancy to prevent complications \u00B7 Timeline: During pregnancy
Recommended retest: Confirm at 12 weeks; test other antiphospholipid antibodies
Got your blood test report?
Upload your PDF and understand ALL your markers in 2 minutes. Plain language. Traffic light status. No medical jargon.
Analyze My Report — FreeFirst report is free. No credit card needed.