Beta-2-glycoprotein I antibodies in patients with thrombosis

The laboratory diagnosis of antiphospholipid antibody syndrome currently requires two consecutive positive results in either lupus anticoagulant or anticardiolipin antibody assays. Antibodies against beta-2-glycoprotein I (abeta2-GPI) are suggested as a new marker for the syndrome. The inclusion of abeta2-GPI in the official diagnostic criteria has so far been precluded owing to lack of an international standard and also technical difficulties. Samples from 5367 consecutive patients sent to a national reference laboratory mainly because of various thrombotic events were studied. An IgG abeta2-GPI ELISA assay was performed in addition to lupus anticoagulant (dRVVT and PTT-LA) and IgG anticardiolipin antibody determinations to evaluate patient groups in which the new assay might be of value. From a total of 90 patients, 2.2% of the samples were abeta2-GPI positive; 51 patients had abeta2-GPI as the only positive antiphospholipid antibody marker; 20 patients had had a venous thrombosis and 14 an arterial thrombosis, 4 had pregnancy complications and 2 had thrombocytopenia. Relatively young patients with cerebrovascular ischaemic events seemed especially to present sole abeta2-GPI positivity. The abeta2-GPI positivity remained fairly constant in the 23 patients from whom follow-up samples were taken. It is concluded that the IgG abeta2-GPI assay seems to be a potentially important additional diagnostic tool for the antiphospholipid antibody syndrome.