What is being tested?

This test detects and measures one or more classes (IgG, IgM, or IgA) of beta-2 glycoprotein 1 antibodies. Beta-2 glycoprotein 1 antibody is one of three primary antiphospholipid antibodies, which are autoantibodies that target the body’s own lipid-proteins (phospholipids) found in the outermost layer of cells (cell membranes) and platelets. It is less common than the other two, cardiolipin antibody and lupus anticoagulant.

Antiphospholipid antibodies interfere with the body’s blood clotting process in a way that is not fully understood. Their presence increases a person’s risk of developing inappropriate blood clots (thrombi) in both arteries and veins. Antiphospholipid antibodies are most frequently seen in those with antiphospholipid syndrome (APS), an autoimmune disorder associated with blood clots (thrombotic episodes), a low platelet count (thrombocytopenia), or with pregnancy complications such as pre-eclampsia and recurrent miscarriages, especially in the 2nd and 3rd trimesters.

One or more antiphospholipid antibodies may also be seen with other autoimmune disorders, such as systemic lupus erythematosus (SLE).

How is it used?

Beta-2 glycoprotein 1 antibody tests are used along with cardiolipin antibody and lupus anticoagulant testing to help diagnose the cause of an unexplained blood clot (thrombotic episode) or recurrent miscarriages, to help diagnose antiphospholipid syndrome (APS), or to detect the autoantibodies in someone with another autoimmune disorder. The beta-2 glycoprotein 1 antibodies are less common than the other antiphospholipid antibodies but the test should be ordered together with cardiolipin antibodies and lupus anticoagulant to make a complete assessment of the syndrome. Anti-beta-2 glycoprotein 1 antibodies are more specific than anticardiolipin antibodies for the diagnosis of APS.

If all three of the initial antiphospholipid antibody tests for the IgG  are negative, but APS is still suspected, then the IgA class of these antibodies may be tested, along with other less common antiphospholipid antibodies, such as anti-phosphatidylserine and anti-prothrombin. However, the value of testing for the IgA class of antiphospholipid antibodies remains controversial. According to the international consensus statement on APS, the presence of the IgA class (either anticardiolipin antibodies or anti-beta-2 glycoprotein 1 antibodies) does not fulfil laboratory criteria for APS diagnosis. In addition there is little clinical evidence that IgM antibodies are of any diagnostic significance.

If an anti-beta-2 glycoprotein 1 antibody is detected, the same test will be repeated about 12 weeks later to determine whether its presence is persistent or temporary. If a person with an autoimmune disorder tests negative for antiphospholipid antibodies, testing may be repeated at a later time to determine if the person has begun to produce antibodies, as they may develop at any time in the course of disease.

When is it requested?

Beta-2 glycoprotein 1 antibody tests and other antiphospholipid antibody testing may be ordered when a person has symptoms suggestive of a blood clot in a vein or artery, such as pain and swelling in the extremities, shortness of breath, and headaches. They also may be ordered when a woman has had recurrent miscarriages. These tests may be ordered initially, along with cardiolipin antibody and lupus anticoagulant testing, or as follow-up tests.

When one of the antibody tests is positive, it will be repeated at least 12 weeks later to determine whether the antibody is temporary or persistent.

When a person with an autoimmune disorder tests negative for anti-beta-2 glycoprotein 1 antibodies, testing may be repeated periodically to screen for antibody development.

What does the result mean?

Anti-beta-2 glycoprotein 1 antibodies are most frequently seen with antiphospholipid syndrome (APS). Current diagnostic criteria for APS are based upon both clinical findings and the persistent presence of one or more antiphospholipid antibodies. If a high level of anti-beta-2 glycoprotein 1 antibodies are detected initially and then again 12 weeks later in a person with signs of APS, then it is likely that the person has the disorder. This is especially true if other antiphospholipid antibodies are also detected.

If a person is negative for anti-beta-2 glycoprotein 1 antibodies but positive for other antiphospholipid antibodies and has signs and symptoms, then that person also likely has APS.

If a person is weakly to moderately positive for anti-beta-2 glycoprotein 1 antibodies and weakly positive or negative for other antiphospholipid antibodies, then the antibody presence may be due to a condition other than APS. If subsequent testing is negative, then it is likely that the antibodies were temporary; this may be seen with an acute infection.

A single positive anti-beta-2 glycoprotein 1 antibody result is not diagnostic of APS, and a negative result does not rule out antiphospholipid antibody development. They just indicate the presence or absence of the antibody at the time of testing.

If a person with another autoimmune disorder, such as systemic lupus erythematosus (SLE), has anti-beta-2 glycoprotein antibodies, they may increase the risk of developing a clot in a blood vessel.

Is there anything else I should know?

One or more antiphospholipid antibodies may be present with a variety of autoimmune disorders.  A person may also have co-existing autoimmune disorders, such as both APS and SLE.

These autoantibodies may also be found temporarily in people with acute infections, HIV/AIDS, some cancers, or with use of drugs such as phenytoin, penicillin, and procainamide.

Common questions

• Should everyone have antiphospholipid testing?

No, this testing is not intended to be a screening tool for the general population. Most people will never need to have this testing performed.

• Can beta-2 glycoprotein 1 antibody testing be performed in my doctor's office?

No, this testing requires specialised equipment and must be done in a laboratory.

• If I have antiphospholipid antibodies, will I definitely develop blood clots?

Not necessarily. They represent a risk factor but cannot predict whether an individual person will have recurrent blood clots. And, if a person does, the presence of the antibodies cannot predict the frequency or severity of clotting.

• Should I tell a new doctor that I have antiphospholipid antibodies?

Yes, this is an important part of your medical history. Your doctor needs this information even if you don't have symptoms in order to tailor any procedures or medical treatment plans around this risk factor.

More information

RCPA Manual: Antiphospholipid syndrome