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Biochemistry

The antiphospholipid antibodies are a heterogeneous group of immunoglobulins (IgG, IgM und IgA) targeted against anionic phospholipids such as diphosphatidylglycerol (cardiolipin), phosphatidylserine (PS), phosphatidylinositol (PI) and phosphatidylglycerol (PG). The binding of the antibodies is dependent on the secondary structure of the phospholipids (lamellar or hexagonal structure). Some antibodies are targeted against phospholipid/protein-complexes. The protein serves as cofactor and was identified as β2-glycoprotein I. These antibodies are autoantibodies. As they target phospholipids essential for the coagulation, they influence the haemostatic balance. The mechanism of formation of these autoantibodies is not yet known. The group of antibodies is very heterogeneous.

Clinical significance

The clinical situation associated with the occurrence of antiphospholipid autoantibodies is defined as antiphospholipid antibody syndrome (APS). The symptoms include recurrent venous and arterial thromboembolic diseases, thrombocytopenia and spontaneous abortions. In the case of a primary antiphospholipid antibody syndrome, no fundamental disease can be recognized. Secondary APS is often associated with autoimmune diseases such as systemic lupus erythematosus (SLE). High antibody concentrations represent an increased risk for thromboembolic diseases. Anticardiolipin antibodies may be found in patients with infectious diseases, especially syphilis, but these have not been correlated with the occurrence of thrombosis. These "infection-anticardiolipin-antibodies" differ from the "autoimmune anticardiolipin-antibodies". The heterogeneity of the antibodies does not allow all antibodies to be identified with a single test. The following tests are the most commonly used:

1. Coagulation test for the determination of lupus anticoagulants (LA): aPTT, dRVVT, KCT, SACT
2. ELISA for the determination of e.g. anti-cardiolipin, anti-phosphatidylserine and anti-β₂-Glycoprotein I-antibodies.

Indication

Differential diagnostic in thrombophilia

Literature

1. Bick R. The Antiphospholipid Thrombosis Syndromes: A Common Multidisciplinary Medical Problem. Clin Appl Thromb Haemost 3, 270-283, 1997.
2. Brandt JT et al. Laboratory Identification of Lupus Anticoagulants: Results of the Second International Workshop for Identification of Lupus Anticoagulants. Thromb Haemost 74, 1597-1603, 1995.
3. Schulman S et al. Anticardiolipin Antibodies Predict Early Recurrence of Thromboembolism and Death among Patients with Venous Thromboembolism following Anticoagulant Therapy. Am J Med 104, 332-338, 1998.
4. Galli M et al. Lupus Anticoagulants and Thrombosis: Clinical Association of Different Coagulation and Immunologic Tests. Thromb Haemost 84, 1012-1016, 2000.
5. Gris JC et al. Antiphospholipid and Antiprotein Syndromes in Non-thrombotic, Non-autoimmune Women with Unexplained Recurrent Primary Early Foetal Loss. Thromb Haemost 84, 228-236, 2000.
6. Pengo V et al. Update of the Giudelines for Lupus Anticoagulant detection. J Thromb Haemost 7, 1737-1740, 2009.
7. Miyakis V et al. International Consensus Statement on an Update of the classification Criteria for Definite Antiphospholipid Syndrome (APS). J Thromb Haemost 4, 295-306, 2006.
8. Brandt JT et al. Criteria for the Diagnosis of Lupus Anticoagulant: An Update. Thromb Haemost 74, 1185-1190, 1995.
9. Goralczyk T, Iwaniec T, Wypasek E, Undas A. False-positive lupus anticoagulant in patients receiving rivaroxaban: 24 h since the last dose are needed to exclude antiphospholipid syndrome. Blood Coagul Fibrinolysis. Jun 26(4), 473-5, 2015.
10. Pengo V, Bison E, Denas G, Jose SP, Bracco A, Banzato A. The paradox of the lupus anticoagulant: history and perspectives. Semin Thromb Hemost. Nov 40(8), 860-5, 2014.