Start Date
Expiration Date
aPS Antibodies
CPT Codes
86148 x 3
Reference Test
ATLAS Test Code

Specimen Information


Gold, SST


0.5 ml

Transport Info

Centrifuge and immediately transfer serum to separate plastic tube

Fasting Required?
Patient Instructions

Reference Range

Less than 20 U/mL


Semi-Quantitative Enzyme-Linked Immunosorbent Assay (ELISA)

Clinical Significance

The antiphospholipid syndrome (APS) is currently recognized as a common risk factor for arterial or venous thromboembolic disease. The presence of high serum levels of antiphospholipid antibodies in patients with APS has been strongly associated with thrombosis, and experimental evidence suggests these antibodies play an important role in this disease. These antibodies have also been associated with a range of clinical conditions including fetal loss, endocarditis, stroke, heart attack, and hemolytic anemia. Antiphospholipid antibodies are a heterogenous group of autoantibodies of IgG, IgM, and IgA classes. These autoantibodies can be directed to anionic phospholipids, phospholipid/protein complexes, and protein cofactors in the absence of phospholipids. It is a standard practice in most clinical laboratories to measure and report both IgG and IgM antiphospholipid antibody levels. Several studies, however, have shown that some patients with antiphospholipid antibodies may have only the IgA isotype. These findings lead to the recommendation to test for IgA antibodies in the routine screening for phospholipid antibodies and/or to look for IgA antibodies in patients with clinical manifestations suggestive of the antiphospholipid syndrome, but without elevated IgG and IgM antibodies. Recent recommended testing algorithms now include three different autoantibodies to properly diagnose APS or to assess the risk for thrombosis or recurrent fetal loss. These include anti-cardiolipin (aCL), anti-Beta-2 glycoprotein I (ß2GPI), and more recently, anti-phosphatidylserine (aPS). Anticardiolipin antibodies (aCL) are a heterogeneous group of antibodies that react with negatively charged phospholipids. One subgroup of autoantibodies directed against cardiolipin is frequently found in systemic lupus erythematosus (SLE) patients, as well as in patients with both venous and arterial thrombosis, thrombocytopenia, and recurrent fetal loss. Patients who present with these latter manifestations have what is termed the "antiphospholipid antibody syndrome" (APS). Another subgroup of anticardiolipin antibodies is found in patients with syphilis and other infectious diseases who have no evidence of coagulation disorders. Studies in the early 1990s identified Beta-2 glycoprotein I (ß2GPI) as a necessary cofactor for antiphospholipid antibody binding in immunoassays. More recent studies, however, have reported that anticardiolipin antibodies derived from autoimmune patients (SLE and APS) were directed only against the ß2GPI molecule when coated on polystyrene plates. There is a potential for traditional anticardiolipin tests to produce false-positive results due to cross-reactivity of phospholipid antibodies present in certain infectious disease samples, most notably syphilis, and with certain other autoantibodies such as antibodies to double- stranded DNA. By eliminating phospholipid from the solid phase and using only ß2GPI, the test becomes more specific for detecting potential coagulation problems. Other important antibodies may be missed, however; thus, testing for aCL and aPS antibodies is still recommended. The third and most recently recognized clinically significant antiphospholipid antibody, aPS, is directed against phosphatidylserine. Unlike cardiolipin, phosphatidylserine is a more physiologically relevant phospholipid due to its presence in cell membranes of endothelial cells and platelets and its role in the coagulation cascade. The detection of anti-phosphatidylserine antibodies has been recommended for the serological diagnosis of antiphospholipid syndrome. Patients with positive results to both cardiolipin and phosphatidylserine are more likely to have clinical complications than those who are positive for only one antibody. These tests should be utilized in patients with unexplained arterial or venous thromboembolic disease or recurring pregnancy loss and in the workup of systemic lupus erythematosus. A lupus anticoagulant panel should probably be run prior to these individual antibody tests. Testing should be repeated in 8-10 weeks for seroconversion or antibody persistence. Test results in themselves are not diagnostic. Assay results are to be interpreted in conjunction with other laboratory tests, as well as with the clinical presentation of the patient.