Beta 2-glycoprotein 1 antibodies (B2GP1)

β2-glycoprotein 1 is a co-factor that binds to phospholipids. Persistent high titre anti-β2-glycoprotein (B2GP1) antibodies or anti-cardiolipin antibodies (ACL) (IgG or IgM) and/or positive lupus anticoagulant (LAC) constitute one of the diagnostic criteria for the antiphospholipid syndrome (APS).

Revised Sapporo/Sydney APS Diagnostic Criteria (Miyakis et al., 2006):
1. Moderate/high titre (>40 ) or above 99th centile IgG or IgM ACL/B2GP1 antibodies or Lupus Anticoagulant (LAC) positive on 2+ occasions and more than 12 weeks apart.
2. Vascular thrombosis
3. Pregnancy morbidity >10 weeks gestation or eclampsia/preeclampsia or 3+ miscarriages <10 weeks. Positive results should be confirmed by repeat testing at least 3 months apart to avoid misdiagnosis. These antibodies can be seen non-specifically during acute infections (e.g. EBV, CMV, HIV, and HCV) and can be induced by certain medications (e.g. phenothiazine, procainamide, and hydralazine). ACL IgM/IgG and B2GP1 IgM/IgG tests are performed together using a multiplex magnetic bead based immunoassay. Screening for APS should also include lupus anticoagulant.

Diagnosis of APS
Investigation of unexplained arterial/venous thrombosis in patients <50 years Investigation of recurrent miscarriage or foetal loss

< 20 GPL-U/mL and < 20 MPL U/mL (reference ranges derived by manufacturer and verified in house)