Beta 2 Glycoprotein I Antibody
The antiphospholipid antibody syndrome (APS) is defined as the occurrence of arterial or venous thrombosis or fetal loss, in association with persistently positive immunoassays for IgG or IgM anticardiolipin antibody (ACA), or coagulation tests for lupus anticoagulant. The APS may be associated with autoimmune disorders, especially SLE (secondary APS) or may occur independently (primary APS). Positivity for anti-beta-2-glycoprotein I (anti-B2GPI) has been shown to be more closely associated with clinical manifestations of APS, including thrombosis, than the ACA assays.
The original assay detected only the IgG isotype of the antibody. Later, an immunoassay for the IgM isotype of anti-B2GPI became available. A recent study evaluated a number of different antiphospholipid antibodies (including both IgG and IgM anti-B2GPI) as predictors of thrombosis, in 100 patients with primary APS, and 90 patients with SLE, 40 of whom had secondary APS. In the patients with SLE, both IgG and IgM anti-B2GPI were strongly associated with the clinical manifestations of APS, with specificity greater than 95%, and positive predictive values (PPV) greater than 90%. In the patients with primary APS, both IgG and IgM anti-B2GPI were strong predictors of thrombosis, especially arterial thrombosis (PPV greater than 90% for both antibodies).
Reference range for both IgG and IgM anti-B2GPI is 0-20 units.
Sample requirement for anti-B2GPI is one red-top tube (minimum 1.0 ml serum).
