Also Known As
Anti-beta-2 glycoprotein 1
β2-glycoprotein 1 antibodies
Beta 2GP1 Ab
Formal Name
Beta-2 glycoprotein 1 antibodies (IgG, IgM, and very rarely IgA)
This article was last reviewed on
This article waslast modified on 5 August 2021.
At a Glance
Why Get Tested?

To help investigate inappropriate blood clot formation; to help determine the cause of recurrent miscarriage; as part of an evaluation for antiphospholipid syndrome (APS)

When To Get Tested?

When you have had one or more unexplained blood clots in a vein or artery; when you have had recurrent miscarriages, especially in the second and third trimesters, if you have a connective tissue disease such as SLE (systemic lupus erythematosus) which can be associated with APS.

Sample Required?

A blood sample taken from a vein in your arm

Test Preparation Needed?


On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you may be able to access your results online. Your GP practice will be able to provide specific details.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, sex, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read Reference Ranges and What They Mean.

What is being tested?

This test detects and measures one or more classes (IgG, IgM, or very rarely IgA) of beta-2 glycoprotein 1 antibodies. Beta-2 glycoprotein 1 antibody is a protein c-factro that binds to phospholipids. Phospholipids are lipid-proteins found in the outermost layer of cells (cell membrane) including blood cells such as platelets. In anti-phospholipid syndrome (APS) autoantibodies are produced that target phospholipid and its co-factors such as B2GP1. Autoantibodies are produced by the body and act against the body. In APS 3 types of auantibodies may be seen; B2GP1, anti-cardiolipin (ACL) 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.

Antiphospholipid antibodies may also be detected in the circulation of patients with other autoimmune disorders, such as systemic lupus erythematosus (SLE).

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is necessary.

Accordion Title
Common Questions
  • How is it used?

    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.

  • When is it requested?

    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.

  • What does the test result mean?

    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.

  • Is there anything else I should know?

    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.

  • 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 test performed.

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

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

  • 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. 

  • 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.