Anticardiolipin Antibodies (ACA)

Antiphospholipid antibodies (APA) are a heterogenous family of auto-antibodies that are associated with an increased risk of venous and arterial thrombosis, recurrent fetal loss and thrombocytopenia. These antibodies are directed against phospholipid-protein complexes and can be IgG, IgM, IgA or mixed isotypes.

Because of their heterogeneity, APA may require several different tests for their detection. Lupus anticoagulants (LA) can be detected by clotting methods, while antibodies directed against Cardiolipin (ACA), Phosphatidylserine (APS) and Beta 2 Glycoprotein I (ABGP) can be detected immunologically.

The Hemostasis and Thrombosis Laboratory recommends that patients with suspected Antiphospholipid Syndrome be tested for LA, ACA, APS and ABGP.

Patients with infections and inflammatory conditions may produce transient ACA that are usually not associated with thrombosis. Antibodies to Anti-beta 2 Glycoprotein I are a more specific marker for increased risk of thrombosis. Nevertheless, markedly elevated ACA titers, especially IgG, are likely to have pathological significance.

APA associated with thrombosis generally persist in the circulation and elevated levels should be confirmed by repeat testing after 2-3 months. APA testing should be part of the evaluation of patients with unexplained thrombosis, thrombocytopenia or recurrent abortion. In addition, the test results may be helpful in determining the intensity and duration of anticoagulant treatment for patients with Antiphospholipid Syndrome and thrombosis.

In the Hemostasis and Thrombosis Laboratory, ACA are detected and quantitated using a plastic support coated with purified cardiolipin that captures the anticardiolipin antibody to be measured. Unbound protein is removed by washing and anti-immunoglobulin (IgG and IgM) horseradish peroxidase-labeled conjugate is added to the wells. After incubation. the unbound conjugate is removed by washing. A substrate is then added, which undergoes a color change in the presence of the conjugated enzyme. After stopping the enzymatic production of colored product, the ACA concentration is determined by extrapolation from a standard curve.

Normal range for Anticardiolipin Antibody is <15 GPL (IgG) units and <18 MPL (IgM) units.