Interpretation and recommended testing for antiphospholipid antibodies.

The antiphospholipid syndrome (APS) is defined by the association of arterial and/or venous thrombosis and/or pregnancy complications with the presence of at least one of the main laboratory-detected antiphospholipid antibodies (aPL) (i.e., lupus anticoagulants [LA], IgG and/or IgM anticardiolipin antibodies [aCL], and IgG and/or IgM anti-β2-glycoprotein I antibodies [aβ2GPI]). During the last decade efforts have been made to improve the harmonization and reproducibility of laboratory detection of aPL and guidelines have been published. The prognostic significance of aPL is being clarified through the fine elucidation of their antigenic targets and pathogenic mechanisms. Several clinical studies have consistently reported that LA is a stronger risk factor for both arterial and venous thrombosis compared with aCL and aβ2GPI. In particular, LA activity dependent on the first domain of β2-glycoprotein I and triple aPL positivity are prognosticators of the thrombotic and obstetric risks. Hopefully, this increasing knowledge will help improve diagnostic and treatment strategies for APS.