Beta-2 Glycoprotein 1 Antibodies

Beta-2 glycoprotein 1 antibody tests are used alongside cardiolipin antibody and lupus anticoagulant testing to help diagnose the cause of unexplained blood clots (thrombotic episodes) or recurrent miscarriages, to help diagnose antiphospholipid syndrome (APS), or as part of the investigation of other autoimmune disorders (e.g. SLE).

If the initial antiphospholipid antibody tests for the IgG and IgM classes are negative then some laboratories will test for IgA antibodies. Although IgA antibodies occur, the value of testing for the IgA class of antiphospholipid antibodies remains controversial and these tests are not routinely available. 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 the laboratory criteria for diagnosis of APS.

If a beta-2 glycoprotein 1 antibody is detected in the blood, the same test will be repeated 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.

Beta-2 glycoprotein 1 antibody tests and other antiphospholipid antibody testing may be requested when a person has symptoms suggestive of a blood clot in a vein or artery, such as pain and swelling in the extremities (hands and feet), shortness of breath due to blood clots, and unexplained 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 beta-2 glycoprotein 1 antibody, testing may be repeated periodically to screen for antibody development.

Beta-2 glycoprotein 1 antibodies are most frequently detected in the blood of patients 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 in the circulation. If a high concentration of beta-2 glycoprotein 1 antibody is detected initially and then again 12 weeks later in a person with signs and symptoms of APS, then it is likely that the person has the disorder. This is especially true if other antiphospholipid antibodies are also detected. This is a confirmatory test, and it is possible to have the antibodies and never have clinical features of APS. Because lots of people are tested with other clinical syndromes, the overall likelihood of having APS with a positive B2GP1 antibody is approximately 32% (i.e. the majority of the patients will have been tested erroneously and will not have APS).

If a person is negative for 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 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 if the patient is suffering from an acute infection.

A single positive 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 beta-2 glycoprotein antibodies present in the circulation, they may increase the risk of developing a clot in a blood vessel.

One or more antiphospholipid antibodies may be present with a variety of autoimmune disorders (see article on autoimmune disorders for a list of examples.) A person may also have co-existing autoimmune disorders, such as 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.

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