Cardiolipin antibodies are the most common antiphospholipid antibody. These autoantibodies target the body’s cardiolipins (substances found in cell membranes and platelets). In patients with SLE, antibodies to cardiolipin (a negatively charged phospholipid) have been associated with arterial and venous thrombosis, thrombocytopenia, and recurrent fetal loss. Patients with the anticardiolipin syndrome have one of the aforementioned clinical features and have antibodies to cardiolipin or a positive lupus anticoagulant test.

The antibodies present to cardiolipin may be of the IgA, IgG, or IgM isotype. Testing for the various antibody isotypes to cardiolipin aids in the diagnosis of the antiphospholipid syndrome in patients with SLE or lupus-like disorders. These tests are also useful for the prognostic assessment of pregnant patients with a history of recurrent fetal loss.

• <12 APL (IgA phospholipid units): absent or none detected

• <15 GPL (IgG phospholipid units): absent or none detected

• <12 MPL (IgM phospholipid units): absent or none detected

1. Collect a 7-mL blood serum sample in a red-topped tube. Observe standard precautions.

2. Label the specimen with the patient’s name, date, and test(s) ordered and place in a biohazard bag for transport to the laboratory.

1. Most patients with antiphospholipid antibody syndrome have moderate (21–80 phospholipid units) or high (>80 phospholipid units) levels of cardiolipin antibodies and are positive for IgG only or IgG and IgM.

2. Elevated values are seen in spontaneous thrombosis and in patients with connective tissue disease.

3. Patients with current or prior syphilis infection may have a false-positive result without the risk for thrombosis.

Pretest Patient Care

1. Explain test purpose and procedure.

2. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.