Review: Laboratory Evaluation of the Antiphospholipid Syndrome

Abstract. Th e antiphospholipid syndrome (APS) was fi rst described in 1986. Th e original association of this hypercoagulable state with anticardiolipin antibodies (aCL) resulted from the synthesis of evidence stemming from laboratory fi ndings in systemic lupus erythematosus (SLE), ie, the frequent occurrence of false-positive VDRL tests and the paradoxical observation of the so-called “lupus anticoagulant ” (LA), an increase in phospholipid (PL)-dependent clotting times. By the early 1990s, it was clear that a co-factor was involved in the reaction of antibodies to PL (aPL) in SLE patients with secondary APS and that this was a hitherto-obscure protein, beta-2 glycoprotein I (β2GPI). In the intervening years, it has been established that β2GPI and other PL-binding proteins such as prothrombin (PT) are relevant antigens in APS and assays for these antigens have been developed, standardized, and applied to subjects with both primary and secondary APS. Measurement and confi rmation of LA activity is based on a stepwise approach and should follow the recommendations of the International Society of Th rombosis and Haemostasis. Although antibodies to various PL-binding proteins have been suggested as diagnostic targets for APS, the current (2006) consensus guidelines recognize only LA, aCL, and anti-β2GPI for the classifi cation of APS