Antiphospholipid Antibodies

Antiphospholipid antibody testing is used to help determine the cause of:

Antiphospholipid antibody testing is used to help determine the cause of an unexplained thrombotic episode, recurrent pregnancy loss, thrombocytopenia, and/or a prolonged PTT test. Since the presence of both lupus anticoagulant and an antiphosphlipid antibody (anticardiolipin or B2GP1 antibody) has a higher specificity for the diagnosis of antiphospholipid syndrome, both tests should usually be performed at the same time.

If an antiphospholipid antibody is detected, the same test(s) should be requested 12 to 24 weeks later to determine whether their presence is persistent or temporary. If a patient with an autoimmune disorder tests negative for antiphospholipid antibodies, they may be retested as these antibodies can develop at any time.

Antiphospholipid antibody testing may be requested when a patient has symptoms suggestive of a thrombotic (clotting) episode, such as pain and swelling in the extremities, shortness of breath, and headaches. It also may be requested when a woman has had recurrent miscarriages and/or as a follow-up to a prolonged PTT test. When one of the tests is positive, it may be repeated several weeks later to determine whether the antibody is temporary or persistent. Antiphospholipid testing may be done when clinical signs suggest the presence of antiphospholipid syndrome. When a patient with an autoimmune disorder tests negative for antiphospholipid antibodies, one or more of the tests may be requested in the future to screen for the development of an antiphospholipid antibody.

Care must be taken when interpreting the results of antiphospholipid antibody tests. A negative result means only that the specific antibody tested was not present at the time of the test. Low to moderate levels of one or more antibodies may occur temporarily due to an infection or drug or may appear as a person ages. These concentrations are often not considered significant but must be examined in conjunction with a patient’s symptoms and other clinical information. In some cases, a person may have one or more classes of a specific antibody present or absent. For instance, they may have significant quantities of IgG and IgM cardiolipin antibodies with or without Beta-2 GP1 antibodies. Moderate to high levels of one or more antiphospholipid antibodies, which persist when tested again 12 to 24 weeks later, indicate the likely continued presence of that specific antibody.

If the tests indicate the presence of the lupus anticoagulant and it persists when retested, then it is likely that the patient is positive for the lupus anticoagulant. Patients who are diagnosed with antiphospholipid syndrome have an increased risk of having recurrent thrombotic episodes, recurrent miscarriages, and thrombocytopenia. Test results cannot predict, however, the likelihood of complications, the type, or the severity in a particular patient. Some will have a variety of recurrent problems while others may never experience any difficulties. Examples of this include an asymptomatic patient who is found to have antiphospholipid antibodies following a prolonged PTT test that is done for another reason (such as a pre-surgical screen), or an asymptomatic older person who has acquired an antiphospholipid antibody.

Occasionally, antiphospholipid testing may be requested to help determine the cause of a positive VDRL/RPR test for syphilis. The reagents used to test for syphilis contain phospholipids and can cause a false positive result in patients with antiphospholipid antibodies.

No. The process that causes them to be produced is not well understood. There are controllable risk factors, however, such as smoking and obesity that also increase your risk of clotting. Addressing these issues may help to lower your overall risk of developing thrombi.