Tests for IgG and IgM cardiolipin antibodies are frequently ordered to help determine the cause of an unexplained thrombotic episode, recurrent miscarriage, or thrombocytopenia. They may be ordered along with lupus anticoagulant testing to help investigate the cause of a prolonged PTT (activated partial thromboplastin time), especially if clinical findings suggest that the patient may have SLE or another autoimmune disorder. If the primary test results are unremarkable but clinical suspicions still exist, then IgA cardiolipin antibody testing may be ordered.

If one or more of the classes of cardiolipin antibodies is detected, then the same test(s) are usually repeated at least 6 weeks apart to help determine whether their presence is persistent or temporary. If a patient with a known autoimmune disorder tests negative for cardiolipin antibodies, they may be retested later as these antibodies may develop at any time in the future.

Cardiolipin antibody testing may be ordered when a patient has symptoms suggestive of a thrombotic episode, such as pain and swelling in the extremities, shortness of breath, or headaches. It may also be ordered when a woman has had recurrent miscarriages, and/or ordered along with lupus anticoagulant testing as a follow-up to a prolonged PTT test. When an IgG, IgM, and/or IgA cardiolipin antibody is detected, then it may be repeated several weeks later to determine whether the antibody is temporary or persistent.

If cardiolipin antibodies are not detected in a patient with an autoimmune disorder, such as SLE, tests may be ordered in the future to screen for their development.

A negative result means only that the cardiolipin antibody class tested (IgG, IgM, and/or IgA) is not present at this time. Since cardiolipin antibodies are the most common of the antiphospholipid antibodies, it is not unusual to find them emerging, temporarily due to an infection or drug, or asymptomatically as a person ages. The low to moderate concentrations of antibody seen in these situations are frequently not significant, but they must be examined in conjunction with a patient’s symptoms and other clinical information.

Moderate to high levels of one or more of the classes of cardiolipin antibodies that persist when tested again 6 weeks later indicate the likely continued presence of that specific antibody.

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