Circulating levels of β₂-glycoprotein I in thrombotic disorders and in inflammation

b(2)- glycoprotein I (beta 2GPI) is a plasma protein suspected to have a role in inhibition of thrombosis. This suspicion is reinforced by the observation that beta 2GPI is the major target for autoantibodies in the antiphospholipid syndrome. However, little is known about its circulating levels in common thrombotic diseases or inflammation. We measured beta 2GPI levels in 344 healthy controls, 58 normal pregnancies, 102 patients with non- haemorrhagic stroke, 121 patients with acute coronary syndrome and 200 patients with elevated C-reactive protein (CRP). In healthy individuals, we found a strong positive correlation between age and beta 2GPI concentration (r = 0.274, P < 0.001) and that beta 2GPI levels fall significantly after the eighth week of pregnancy (P = 0.002). We also found significantly reduced levels of beta 2GPI in patients with stroke and in elderly patients with myocardial syndrome (P = 0.013 and 0.043). However, in neither group did beta 2GPI levels change in the following six months, suggesting that the reduced levels were not a transient post-event phenomenon. In patients with inflammation, beta 2GPI levels showed a significant negative correlation with CRP (r = -0.284, P < 0.001) and positively correlated with albumin and transferrin (r = 0.372 and 0.453, respectively with P < 0.001 for both). Furthermore, the largest reduction in beta 2GPI levels occurred in patients with the highest CRP values (P < 0.001).