In medicine, antiphospholipid syndrome (APS) is the "presence of antibodies directed against phospholipids (antiphospholipid antibody). The condition is associated with a variety of diseases, notably systemic lupus erythematosus and other connective tissue diseases, thrombopenia, and arterial or venous thromboses. In pregnancy it can cause abortion. Of the phospholipids, the cardiolipins show markedly elevated levels of anticardiolipin antibodies (anticardiolipin antibody). Present also are high levels of lupus anticoagulant (lupus anticoagulant inhibitor)."
The following antibodies are associated with the antiphopholipid syndrome; however, these antibodies may be present transiently in normal individuals.
- Lupus anticoagulant antibodies. These are detected by prolong clotting times such as partial thromboplastin time (aPTT) or dilute activated partial thromboplastin time (dAPTT) or dilute Russell viper venom time (dRVVT). These are more specific tests. These antibodies may interact with other risk factors such as smoking and estrogens.
- Anticardiolipin antibodies. These are antibodies to a phospholipid and are detected by immunoassays (usually enzyme-linked immunosorbent assays).
- Anti–β2-glycoprotein I (formerly known as apolipoprotein H). These are antibodies to a phospholipid-binding protein and are detected by immunoassays (usually enzyme-linked immunosorbent assays).
More recently identified antibodies are against the vimentin/cardiolipin complex. Vimentina is a protein that binds to cardiolipin in vitro
According to the Sapporo criteria, patients must have both:
- Some form of embolism and thrombosis
- Abnormal antibodies
Laboratory criteria according to an international consensus statement are:
- "Lupus anticoagulant present in plasma on two or more occasions at least 12 weeks apart."
- "Medium or high titre (>40 IgG or IgM phospholipid units (1 unit is 1 µg of antibody), or >99th centile) of IgG or IgM anticardiolipin antibody in serum or plasma on two or more occasions, a least 12 weeks apart, measured by standardised enzyme linked immunosorbent assay (ELISA)."
- "Medium or high titre (>40 IgG or IgM phospholipid units, or >99th centile) of IgG or IgM anti-ß2 glycoprotein I antibody in serum or plasma on two or more occasions, a least 12 weeks apart, measured by standardised ELISA, according to recommended procedures."
- Anonymous (2015), Antiphospholipid syndrome (English). Medical Subject Headings. U.S. National Library of Medicine.
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