Lupus anticoagulants (LAs) are a type of antibody produced by the immune system. While antibodies usually attack foreign substances, LAs instead attack phospholipids, which are a key component of cell membranes. LAs relate to an immune system disorder known as antiphospholipid syndrome, and a blood test can detect their presence.

Despite its name, lupus anticoagulant does not only occur in people with lupus, nor is it mainly associated with bleeding. The term originates from the observation that blood samples from individuals with systemic lupus erythematosus (SLE) could not clot within an appropriate time.

LAs are one of the antiphospholipid antibodies that can lead to an immune system disorder called antiphospholipid syndrome. Phospholipids play a vital role in blood clotting, and these antibodies can increase the risk of thrombosis. A series of blood tests can help identify if LAs are present and enable a doctor to create a suitable treatment plan.

In this article, we look at what lupus anticoagulants are, causes and risk factors, symptoms, and diagnosis. We also look at treatment options and when to contact a doctor.

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Scientists first coined the term “lupus anticoagulant” to describe the occurrence of plasma cells in people with SLE that fail to clot in a typical amount of time. Despite what the name suggests, LAs are associated with an increased risk of blood clotting rather than bleeding. Additionally, while LAs frequently relate to SLE, a person can have the antibodies without having lupus.

LAs are an antiphospholipid antibody. Usually, antibodies are protective proteins produced by the immune system that act in response to foreign objects. They attach to a molecule on the surface of the foreign body, known as an antigen, and help remove it from the body.

Instead of protecting the immune system, lupus anticoagulants attack healthy cells and cell proteins. They specifically target the phospholipid element of the cell membrane. Phospholipids are a type of fat present in all living cells, including blood cells and the lining of blood vessels. LAs interfere with the clotting process, which can increase the risk of complications.

Experts do not know the exact cause of LAs but conclude that factors such as infections, medications, and autoimmune conditions can result in the development of these antibodies.

LAs are often present in people with other autoimmune conditions, especially SLE. However, they can also occur with infections such as HIV, hepatitis, and malaria, as well as in those taking certain medications, such as procainamide and chlorpromazine.

Some evidence suggests that the incidence of LAs increases with age and is more common in females.

People with LAs may show no symptoms. In some cases, certain triggers may cause blood clots to develop. These can include:

LAs are the antiphospholipid antibody most strongly associated with thrombosis, which refers to the blockage of veins or arteries by blood clots. Depending on where the clot forms, a person may experience different symptoms.

A blood clot in the heart or lung area can cause:

  • breathing difficulty
  • pain in the chest
  • dizziness
  • fatigue
  • sweating heavily

A blood clot in an arm or leg can cause:

  • numbness in the leg or arm
  • pain
  • swelling
  • discoloration or redness

A blood clot in the kidneys or stomach can cause:

Blood clots can be life threatening if a person does not receive suitable treatment.

Other potential complications may include:

  • stroke
  • transient ischemic stroke
  • acquired thrombophilia
  • pregnancy loss

There is no single test to detect lupus anticoagulant, but there is a series of tests that can help a doctor make a diagnosis. A doctor may suggest these tests if a person has an unexpected blood clot or has had more than one miscarriage. A doctor will draw blood to perform these tests.

There is a three-step procedure to detect the presence of LAs: screening, mixing, and confirmation. These tests measure the time it takes for blood to clot. They operate on the principle that LAs are a nonspecific inhibitor, so they do not target a specific coagulation factor but bind to the assay’s phospholipids, prolonging the tests.

A technician will typically use either an activated partial thromboplastin time (aPTT) test or a dilute Russell’s viper venom test (DRVVT) for the diagnostic procedure. If the initial screening test takes longer than usual, the technician will proceed to the mixing test. This involves mixing a person’s plasma with pooled normal plasma from donors. Doing so can help determine if the delay is due to a specific coagulation deficiency or a nonspecific inhibitor.

In the third test, a technician will include additional phospholipids and compare this sample to a control sample. If LAs are present, then the test will be quicker. A technician will also use these tests to rule out possible diagnoses, such as clotting factor deficiencies.

As these sequential tests involve blood samples, there are relatively few risks, and a person does not need to prepare beforehand.

If a person has lupus anticoagulant but does not have symptoms, such as blood clots, they may not require any immediate treatment. A person can take measures to avoid potential triggers for blood clots, such as smoking and inactivity.

Treatments for blood clots may include:

  • Blood-thinning medications: Common types include warfarin and heparin, and a doctor may also suggest aspirin. Some people may only need to take these medications for a few months, while others will need to stay on them for the long term.
  • Plasma exchange: This is a process in which a machine separates blood plasma containing lupus anticoagulants from other blood cells. The healthy plasma then replaces plasma containing lupus anticoagulants.
  • Lifestyle changes: Some people may consider adopting lifestyle changes such as getting regular exercise, stopping smoking, eating a nutritious diet, and maintaining a moderate weight.

A person should seek medical help if they notice any symptoms of a blood clot, such as:

  • shortness of breath
  • numbness or pain in the arms or legs
  • skin that looks paler than usual in the arms or legs
  • swelling or redness in the leg
  • repeated miscarriages

Lupus anticoagulants are a type of antibody that attacks healthy cells and cell proteins. They target essential components of cell membranes called phospholipids that play a role in blood clotting. These antibodies often relate to an immune system disorder called antiphospholipid syndrome.

The presence of LAs can increase the risk of blood clotting, which can be life threatening if a person does not seek treatment. A person can receive a diagnosis if they undergo a series of tests that measure the amount of time it takes for blood to clot. Treatment options may include blood-thinning medication and lifestyle changes.