Overview of Lupus Anticoagulant

Lupus anticoagulant (LA) is an antiphospholipid antibody found in many people with lupus. LA increases your blood's ability to clot. Therefore, if you have this antibody, you have a greater risk of experiencing a blood clot. You do not need to have lupus to have LA. 

According to the Johns Hopkins Lupus Center, antiphospholipid antibodies are antibodies directed against:

  • Cell membrane components called phospholipids
  • Certain blood proteins that bind with phospholipids
  • Complexes that are formed when proteins and phospholipids bind
Blood clotting under a microscope

About 30 percent of people with lupus have antiphospholipid antibodies. Antiphospholipid antibodies interfere with the normal function of blood vessels and can lead to narrowing of the blood vessels or blood clots. These complications can lead to stroke, heart attack, and miscarriage.

It's Not Always Related to Lupus

The antiphospholipid antibody LA was first discovered in systemic lupus erythematosus patients in the 1940s. Today, healthcare providers recognize that LA also occurs in people with other autoimmune diseases (such as inflammatory bowel disease), certain infections and tumors, as well as in people who take certain medications, including phenothiazines, phenytoin, hydralazine, quinine, or the antibiotic amoxicillin.

The name LA (lupus anticoagulant) is misleading because it suggests that the antibody increases bleeding. In reality, LA helps the blood to clot. In fact, about 50 percent of lupus patients with LA will experience a blood clot over a twenty-year period of time, which makes the presence of this antibody dangerous.

If you have LA, you should be especially aware of the signs and symptoms of a blood clot including:

  • Leg swelling or redness
  • Shortness of breath
  • Pain, numbness, and pallor in an arm or leg
  • Increased risk of cardiovascular disease
  • Increased risk of pre-eclampsia and miscarriage

Testing for LA

Coagulation tests, which measure how long it takes blood to clot, are used to detect LA. Healthcare providers treating lupus patients usually start with a coagulation test called the activated partial thromboplastin time (aPTT). 

If the results of the aPTT are normal, healthcare providers will use a more sensitive test to be sure. Usually, this is the modified Russell viper venom time (RVVT), which uses phospholipid and venom from a Russell viper snake to detect LA. Other sensitive coagulation tests that may be used are platelet neutralization procedure (PNP) and kaolin clotting time (KCT).

Preventing Blood Clots

People who test positive for LA are often prescribed blood thinners to help prevent clots, but only when abnormal clotting presents itself. Steroids may be prescribed to assist in lowering antibody levels.

With the right therapy, complications from LA are manageable.

There are some things you can do to prevent blood clots if you have LA:

  • Avoid estrogen-based birth control pills and hormone treatments for menopause
  • Don't smoke or use other tobacco products
  • Don't sit or lie down for extended periods other than when you're asleep
  • When traveling, get up periodically to keep your blood flowing
  • Move your ankles up and down when you can't move around

If you are concerned about blood clots, speak to your healthcare provider about LA and your personal risk of developing blood clots. Your healthcare provider may have recommendations, specific to you, which can help lower your risk. 

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5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Johns Hopkins Lupus Center. Antiphospholipid Antibodies.

  2. Fei X, Wang H, Jiang L, Zhao T, Cheng M, Yuan W. Clinical and Prognostic Significance of Lupus Anticoagulant Measurement in Patients With Lung Cancer. Technol Cancer Res Treat. 2017;:1533034617714150.  doi:10.1177/1533034617714150

  3. National Heart, Lung, and Blood Institute. Antiphospholipid Antibody Syndrome.

  4. Lupus Foundation of America. Antiphospholipid Antibodies Syndrome. Updated March 21, 2016.

  5. U.S. National Library of Medicine. MedlinePlus. Lupus Anticoagulants and Antiphospholipid Antibodies. Updated January 10, 2019.