Anti-beta2-glycoprotein I antibodies--when and how should they be measured?

The biological criteria of the antiphospholipid syndrome defined at the Sapporo meeting in 1998 included the presence of lupus anticoagulant (LA) and/or anticardiolipin antibodies at medium and high titers. During the 48th SSC meeting held in Boston July 2002, it was proposed to modify these criteria. Four patient groups were defined, the first one comprising LA and anti-beta2glycoprotein I antibodies (abeta2GPI), the second one LA only, the third one abeta2GPI only and the fourth one other antiphospholipid antibodies such as antiprothrombin, anticardiolipin, antiphosphatidylethanolamine, etc. This proposition raised the issue of the association of abeta2GPI with APS clinical criteria (thrombosis and pregnancy morbidity). In some studies, a strong association between IgG abeta2GPI and thrombosis was found, whereas in others this association could not be demonstrated. In the obstetrical field, few studies are available and no clear conclusion can be drawn yet. However, for thrombosis or pregnancy morbidity, it has been shown that in up to 10% of patients, abeta2GPI are the sole antibodies present and therefore the diagnosis of APS would be missed in these patients. In addition, some studies suggest that the severity of disease is dependent on the number of positive tests and on their titers. We recommend abeta2GPI assays to be included in the panel of antiphospholipid screening tests. However, the standardisation of abeta2GPI assays has to be improved in order to ensure better comparability between the studies.