Beta‐2‐glycoprotein I antibodies in patients with thrombosis

Abstract

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 (aβ2‐GPI) are suggested as a new marker for the syndrome. The inclusion of aβ2‐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 aβ2‐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 aβ2‐GPI positive; 51 patients had aβ2‐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 aβ2‐GPI positivity. The aβ2‐GPI positivity remained fairly constant in the 23 patients from whom follow‐up samples were taken. It is concluded that the IgG aβ2‐GPI assay seems to be a potentially important additional diagnostic tool for the antiphospholipid antibody syndrome.