Beta 2 Glycoprotein I Antibody

Antiphospholipid antibodies (APL) are a family of autoantibodies that recognize various combinations of phospholipids, phospholipid-binding proteins or both. These antibodies include lupus anticoagulants, detected by coagulation assays, and anticardiolipin antibodies (ACA), detected by immunoassays. Despite frequent concordance between these types of antibodies, they are not identical.  The antiphospholipid antibody syndrome (APS) refers to the clinical association between these antibodies and a syndrome of hypercoagulability. The syndrome may be “primary”, in patients without another autoimmune disease, or “secondary”, associated with an autoimmune disorder, especially systemic lupus erythematosus. Between 20 and 30% of patients with systemic lupus erythematosis have persisten antiphospholipid antibodies that are associated with clinical sequelae. 

The revised Sapporo criteria for classification of the antiphospholipid syndrome state that the disease is characterized by thrombosis, pregnancy complications, or both in patients with persistent antiphospholipid antibodies (lupus anticoagulant, anticardiolipin antibodies, or anti-beta-2 glycoprotein 1 antibodies).

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. In 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).

Detection of IgG or IgM anti-B2GPI can add credence to a diagnosis of APS, especially in borderline cases.

Anti-beta-2 glycoprotein 1 antibodies are detected by enzyme immunoassay. Reference range for both IgG and IgM anti-B2GPI is 0-15 units. 

Sample requirement for anti-B2GPI is one red-top tube (minimum 1.0 ml serum). 

For more information, please see Antiphospholipid Antibody Syndrome.

References

Miyakis S, et al. International consensus statement on an update of the classification criteria for definite antiphospholipid syndrome (APS). J Thromb Haemost. 2006;4(2):295-306.

Audrain MAP, et al. Value of autoantibodies to beta(2)-glycoprotein 1 in the diagnosis of antiphospholipid syndrome. Rheumatology, 2002;41(5):550-553