What Is Lupus Anticoagulant?

This Antibody Puts Patients At Risk for Blood Clots

Blood clotting under a microscope.
Blood clotting under a microscope.. STEVE GSCHMEISSNER/Getty Images

Lupus anticoagulant (LA) is a specific antibody found in many lupus patients. Lupus anticoagulant increases the ability of the blood to clot, so if you are found to have this antibody, you are at greater risk of a blood clot.

Understanding Antiphospholipid Antibodies

More specifically, lupus anticoagulant is an antiphospholipid antibody. 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

About 50 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.

Lupus Anticoagulant - A Confusing Name

You do not need to have lupus to have LA. The antiphospholipid antibody lupus anticoagulant was first discovered in systemic lupus erythematosus patients in the 1940s. Today, doctors 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 lupus anticoagulant is misleading because it suggests that the antibody increases bleeding. In reality, lupus anticoagulant helps blood to clot. In fact, about 50 percent of lupus patients with lupus anticoagulant will experience a blood clot over a twenty-year period of time, which makes the presence of this antibody dangerous.

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

  • Swelling or redness in the leg
  • Shortness of breath
  • Pain, numbness, and pallor in an arm or leg

Tests for Lupus Anticoagulant

Coagulation tests, which measure how long it takes blood to clot, are used to detect lupus anticoagulant.

Physicians treating lupus patients usually start with a coagulation test called the activated partial thromboplastin time (aPTT).

If the results of the aPTT are normal, doctors 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 lupus anticoagulant. 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 maybe be prescribed to assist in lowering antibody levels.

With the right therapy, complications from lupus anticoagulant are manageable.

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

  • Women should avoid most birth control pills or 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 - get up periodically to keep your blood flowing.
  • Move your ankles up and down when you can't move around.

Sources:

Antiphospholipid Antibodies. The Johns Hopkins Lupus Center.

Lupus Anticoagulants and Antiphospholipid Antibodies. MedlinePlus. U.S. National Library of Medicine. January 20, 2015.

Antiphospholipid Antibodies. Lupus Foundation of America. August 2008.

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