HomeAntiphospholipid Antibodies and Systemic Lupus Erythematosus
Michelle Petri, M.D., M.P.H.
Associate Professor of Medicine
The John Hopkins University School of Medicine
Baltimore, MD

What Are Antiphospholipid Antibodies?

There are several kinds of antiphospholipid antibodies.  The most widely measured are the lupus anticoagulant and anticardiolipin antibody.  These antibodies react with antiphospholipid, a type of fat molecule that is part of the normal cell membrane.  Lupus anticoagulant and anticardiolipin antibody are closely related, but are not the same antibody.  This means that someone can have one and not the other.  There are other antiphospholipid antibodies, but they are not commonly measured.

How Common Are Antiphospholipid Antibodies?

As with other autoantibodies (antibodies directed against one’s self) in lupus, the antiphospholipid antibodies can come and go in any individual patient.  It turns out that there are many ways to measure these antibodies and different methods may not always give the same result.  For example, in different studies, 8 to 65 percent of lupus patients have the lupus anticoagulant, and 25 to 61 percent have anticardiolipin antibody.  Normal people can also have these antibodies.  For example, two percent of normal young women have anticardiolipin antibody.  These antibodies were first discovered in people who have lupus, but it is not necessary to have lupus to have these antibodies.  In fact, in most studies, over 50 percent of people  with these antibodies do not have lupus.  We do not understand why a person’s immune system begins to manufacture these antibodies.

Why Are Antiphospholipid Antibodies Important?

The presence of both the lupus anticoagulant and anticardiolipin antibody is increased in lupus patients who have had thrombotic (blood clotting) complications such as deep venous thrombosis (“thrombophlebitis”), stroke, gangrene, and heart attack.  Studies suggest that the presence of these antibodies may also increase the future risk of thrombotic events.  Anticardiolipin antibody has been found to be increased in pregnant women with lupus who have had miscarriages.  The combination of thrombotic problems, miscarriages, and a low platelet count has been called the “Antiphospholipid Antibody Syndrome.”  It is not necessary to have lupus to have the antiphospholipid antibody syndrome.  It is important for doctors to realize this and to check people who have had a stroke, heart attack, or miscarriage for no known reason to see if they have these antibodies.

Antiphospholipid antibodies interfere with the normal function of blood vessels, both by causing narrowing ad irregularity of the vessel (called “vasculopathy”), and by causing clots in the vessel (called “thrombosis”).  These blood vessel problems can then lead tocomplications such as stroke, heart attack, and miscarriage.

How Do Doctors Test For Antiphospholipid Antibodies?

Blood tests are used to identify antiphospholipid antibodies.  Specialized tests which measure blood clotting (coagulation tests) are used to find the lupus anticoagulant.  The activated partial thromboplastin time (aPTT) is a widely available blood clotting test that is often used.  If the aPTT is normal, more sensitive coagulation tests should be done to test for the lupus anticoagulant.  These more sensitive tests include the modified Russell viper venom time (RVVT), the platelet neutralization procedure (PNP), ant the kaolin clotting time (KCT).  If the clotting test is prolonged (the number of seconds that it takes the blood to clot is longer), the physician will suspect that the lupus anticoagulant is present.  This is confusing, because even though the blood takes longer to clot in the test tube, the blood actually clots more easily in the person’s body.

The anticardiolipin antibody in measured in an ELISA test.  There are many classes of anticardiolipin antibody (IgG, IgM, IgA).  It is possible to test for all of these antibody classes at once or the physician may wish to test for each separately.  The IgG type ofanticardiolipin antibody is the type that is not often associated with complications.  Sometimes, there are technical difficulties with the IgM test, making it more difficult to interpret the results of this test.  Some lupus patients with very high IgM anticardiolipin antibody have a problem called hemolytic anemia, in which their immune system attacks their red blood cells.

Since Antiphospholipid Antibodies Can Come And Go, How Often Should Doctors Check For Them In Lupus Patients?

There are no current recommendations of the timing of repeat tests.  Certainly the antiphospholipid antibodies should be checked in people who have had thrombotic problems, miscarriages, or low platelet counts.

What Is The Treatment For A Person Who Has Antiphospholipid Antibodies?

If a person has the lupus anticoagulant or anticardiolipin antibody, but has never had a thrombotic complication, treatment is not currently recommended.  If a patient has had a thrombotic complication and has these antibodies, treatment may depend on where the clot (thrombosis) occurred.  In general, treatment consists of “thinning” of blood to prevent future clots, using either aspirin or warfarin (coumadin).

How Successful Is Treatment In People Who Have Had A Thrombosis (Clot) In Association With These Antibodies?

Some individuals who had initially been treated with aspirin have had a second episode of thrombosis and have been treated with warfarin (coumadin).  A few of these patients had a second episode of thrombosis while on warfin.  However, treatment with warfarin appears to be successful overall.  The length of time that this treatment is necessary is unclear.  Many physicians recommend long-term or even life-long treatment to prevent future episodes of thrombosis.

If A Woman Has Antiphospholipid Antibodies And Is Pregnant, How Is It Treated?

If the woman has antiphospholipid antibodies and is pregnant for the first time, or has had normal pregnancies in the past, no treatment may be advised.  However, if the woman has had miscarriages in the past, several different treatment regimens are available, including aspirin, Prednisone, and/or subacutaneous shots of a blood thinner called heparin.  Pregnancies in women with antiphospholipid antibodies are considered to be “high risk pregnancies.”

It is necessary for the obstetrician or gynecologist to work closely with the rheumatologist or other physician who evaluates a woman with miscarriages for antiphospholipid antibodies.  Miscarriages, especially early in pregnancy, are not rare.  Women who have had multiple miscarriages should be checked to see if they have antiphospholipid antibodies as part of an overall obstetric evaluation for causes of miscarriage.

How Successful Is Treatment In Lupus Patients Who Have Had A Miscarriage In Association With these Antibodies?

The treatment of pregnant women with antiphospholipid antibodies to prevent a possible miscarriage is not well understood at the current time.  Some women are helped by combinations of aspirin, Prednisone, and/or subcutaneous heparin, whereas other women continue to have miscarriages even when they are taking these medications.  Subcutaneous heparin is less likely then Prednisone to cause diabetes and an increase in blood pressure during pregnancy.  Other treatments, including plasmapheresis or intravenous gammaglobulin, may be considered in individual cases.