The diagnosis of the antiphospholipid syndrome

The concurrence of antiphospholipid (aPL) antibodies and thrombosis or pregnancy loss defines the 'antiphospholipid syndrome' (APS). The Sydney update of the classification criteria for definite APS diagnosis introduced numerous ameliorations to the previous preliminary consensus statement. Clinical criteria are now better defined as vascular thrombosis must be diagnosed on the basis of objective criteria. Moreover,additional risk factors for thrombosis or pregnancy loss must be taken into account before the diagnosis is made and should be described in detail in scientific reports. As far as laboratory criteria are concerned,the lack of standardization and the misinterpretation of results remain major problems often leading to overdiagnosis. A single positive test result out of the possible assays determining aPL antibodies (Lupus Anticoagulant, LAC, anticardiolipin, aCL and anti. beta2-Glycoprotein I, beta2-GPI, antibodies) is still sufficient,according to the Sydney criteria, to justify a diagnosis of APS. Nevertheless single test positivity may result in overdiagnosis or identification of low risk patients and use of all three tests seems more reasonable. Multiple positivity or (better) triple positivity in our experience allows for the identification of high risk patients for possible recurrence. In the near future, coagulation tests discriminating between a beta2-GPI and anti-prothrombin LAC may be useful in identifying high risk patients.