At a Glance

Why Get Tested?

To help diagnose antiphospholipid syndrome (APS); to help diagnose the cause of an unexplained blood clot (thrombotic episode or venous thromboembolism); to help determine the cause of recurrent miscarriages in women

When To Get Tested?

When you have signs and symptoms of APS and/or have had one or more unexplained blood clots in a vein or artery; when you have had more than one miscarriage, especially in the second and third trimesters of pregnancy

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?


What is being tested?

Beta-2 glycoprotein 1 antibody is an autoantibody that is associated with inappropriate blood clotting. This test detects and measures beta-2 glycoprotein 1 antibodies in the blood.

Beta-2 glycoprotein antibody is considered one of the primary autoantibodies called antiphospholipid antibodies that mistakenly target the body’s own lipid-proteins (phospholipids) found in the outermost layer of cells (cell membranes) and platelets. This test is often ordered along with tests for other antiphospholipid antibodies, including cardiolipin antibody and lupus anticoagulant.

Antiphospholipid antibodies interfere with the body’s blood clotting process in a way that is not fully understood yet. They increase the risk of developing inappropriate blood clots (thrombi) in both arteries and veins.

Antiphospholipid antibodies most frequently develop in people with the autoimmune disorder called antiphospholipid syndrome (APS). This condition is associated with widespread blood clots (thrombotic episodes), a low platelet count (thrombocytopenia), or with pregnancy complications such as pre-eclampsia and recurrent miscarriages, especially in the second and third trimesters.

Also, some people with autoimmune disorders such as lupus (systemic lupus erythematosus, SLE) may begin to produce one or more of these autoantibodies, which can put them at risk of forming blood clots in blood vessels.

Common Questions

How is the test used?

Beta-2 glycoprotein 1 antibody tests are primarily used along with cardiolipin antibody and lupus anticoagulant testing to help diagnose:

  • Antiphospholipid syndrome (APS)
  • The cause of an unexplained blood clot (thrombotic episode)
  • The cause of recurrent miscarriages in women

Sometimes the test may be used to determine whether you have developed these autoantibodies if you have another autoimmune disorder, such as lupus.

Laboratory tests can detect three different classes of these autoantibodies: IgG, IgM, and IgA. If the initial antiphospholipid antibody tests for the IgG and IgM classes are negative but APS is still strongly 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 beta-2 glycoprotein 1 antibodies) does not fulfill laboratory criteria for APS diagnosis.

When is it ordered?

This testing may be ordered when you have signs and symptoms of excessive clotting or antiphospholipid syndrome (APS), such as:

  • A blood clot in a blood vessel, for example, deep vein thrombosis (DVT)
  • Stroke or transient ischemic attacks (also known as TIA or “mini strokes”)
  • Repeated miscarriages or pregnancy complications such as pre-eclampsia

This test may sometime be done when you have been diagnosed with an autoimmune disorder and your healthcare practitioner wants to determine whether you have developed the autoantibody.

What does the test result mean?

Your health care practitioner will consider the results of your tests along with other factors, such as medical history, physical exam, and signs and symptoms.

A positive beta-2 glycoprotein 1 antibody test may indicate that you have antiphospholipid syndrome (APS), as they are most frequently seen with this condition. If the test is positive, it will be repeated about 12 weeks later to determine whether it is persistent or temporary.

Currently, health care practitioners diagnose APS based on both clinical findings and the persistent presence of one or more antiphospholipid antibodies. A high level of beta-2 glycoprotein 1 antibody that is tested and confirmed as positive 12 weeks later means that it is likely that you have APS. This is especially true if other antiphospholipid antibody tests are positive.

If you are tested negative for beta-2 glycoprotein 1 antibodies but positive for other antiphospholipid antibodies and have signs and symptoms, you likely have APS. If the test is weakly to moderately positive for beta-2 glycoprotein 1 antibodies and weakly positive or negative for other antiphospholipid antibodies, it means the antibody may be due to a condition other than APS. If repeat testing is negative, then it is likely that the antibodies were temporary. These autoantibodies may be found temporarily in people with acute infections, HIV/AIDS, some cancers, or with use of drugs such as phenytoin, penicillin, and procainamide.

If you have an autoimmune disorder, such as lupus (systemic lupus erythematosus, SLE), and test positive for beta-2 glycoprotein antibodies, you may have increased risk of developing a clot in a blood vessel. 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 lupus.

If you have an autoimmune disorder and test negative for antiphospholipid antibodies, testing may be repeated at a later time to determine if you have started to produce them because they may develop at any time in the course of the disease.

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

Not necessarily. The antibodies increase your risk of blood clots but that does not mean you will have blood clots. And, if you do develop a clot, the presence of the antibodies cannot predict the frequency or severity of clotting.

Should I tell a new healthcare practitioner that I have antiphospholipid antibodies?

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


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