Diagnosis
Antiphospholipid syndrome is diagnosed using either liquid-phase coagulation assays to detect lupus anticoagulant or solid phase ELISA (enzyme-linked immunosorbent assay) to detect anti-cardiolipin antibodies or anti-apolipoprotein antibodies.Genetic thrombophilia is part of the differential diagnosis of APS and can coexist in some patients with APS. Presence of genetic thrombophilia may determine the need for anticoagulation therapy. Thus, genetic thrombophilia screening can consist of:
Screening for factor V Leiden variant and the prothrombin G20210A and MTHFR mutations. Measuring serum levels of protein C, free and total protein S, factor VIII, antithrombin, plasminogen, tissue plasminogen activator and plasminogen activator inhibitor-1.Antiphospholipid antibodies do not recognize isolated cardiolipin, but bind to a cardiolipin-β2GPI (apolipoprotein H) complex. The use of testing for antibodies specific for individual targets of aPL such as β2 glycoprotein 1 and phosphatidylserine is currently under debate. Lupus anticoagulant
This is tested for by using a minimum of two coagulation tests that are phospholipid-sensitive, due to the heterogeneous nature of the lupus anticoagulant antibodies. The patient on initial screening will typically have been found to have a prolonged partial thromboplastin time (PTT) that does not correct in an 80:20 mixture with normal human plasma (50:50 mixes with normal plasma are insensitive to all but the highest antibody levels). The PTT (plus 80:20 mix), dilute Russells viper venom time, kaolin clotting time, dilute thromboplastin time, silica clotting time and prothrombin time (using a lupus-sensitive thromboplastin) are the principal tests used for the detection of lupus anticoagulant.
Criteria
Classification with APS requires evidence of both one or more specific, documented clinical events (either a vascular thrombosis and/or adverse obstetric event) and the confirmed presence of a repeated aPL. The Sapporo APS classification criteria (1998, published in 1999) were replaced by the Sydney criteria in 2006.