Lupus anticoagulants are antibodies against phospholipids (substances in the lining of cells) that prevent blood clotting in a test tube. Persons with these antibodies may have an abnormally high risk of blood clotting.

See also: Antibody

Lupus anticoagulants are usually found in persons with autoimmune diseases, such as systemic lupus erythematosus (SLE). They may also be found in persons who take certain medications, including phenothiazines, phenytoin, hydralazine, quinine, amoxicillin, and birth control pills. Persons with inflammatory bowel disease (Crohn's disease and ulcerative colitis), infections, and certain tumors may have lupus anticoagulants.

Some people have no risk factors for this condition. In some cases, it is linked to an increased risk of blood clots and may be the cause of recurrent miscarriages.

• Blood clots
• Recurrent miscarriages

There may be no symptoms.

• Partial thromboplastin time (PTT)
• Thromboplastin inhibition test
• Russell viper venom time