Antiphospholipid (APL) antibodies can be detected in as many as 1% to 5% of unselected individuals.1,2 These antibodies are a common acquired cause of increased thrombotic risk (currently obesity is the most common acquired cause of hypercoagulability.3-9 The term “antiphospholipid syndrome” (APS) refers to a spectrum of clinical conditions that is associated with the presence of antiphospholipid antibodies. Both clinical and laboratory features must be present for the diagnosis of APS to be made.8-10 Any one or more of the conditions discussed below can occur in patients with the antiphospholipid syndrome.
Antiphospholipid antibodies can be subclassified into several clinical categories:
A variety of therapeutic drugs can induce the production of antiphospholipid antibodies
calcium channel blockers
Individuals with drug-induced antiphospholipid antibodies that persist after the drug treatment is ended experience an increased risk of thrombosis.5
Often observed during the convalescent phase of acute bacterial and viral infection
Often observed in individuals with syphilis
Generally not associated with an increased risk of clinical complications as these antibodies tend to be directed against phospholipid rather than phospholipid-binding proteins
Note: Because it is not possible to distinguish infection-induced antiphospholipid antibodies from clinically significant antiphospholipid antibodies, all patients who test positive for antiphospholipid antibodies should be retested after 12 or more weeks to rule out transient antibodies.10
Antiphospholipid antibodies can be detected indirectly with tests that are based on their effect on clot-based, in vitro coagulation assays (ie, lupus anticoagulants) or directly by solid-phase immunoassay.13 Due to the heterogeneity of antibodies associated with APS, both clotting and solid-phase immunoassay testing is recommend when APS is suspected.4,9
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