Anti-beta2-Glycoprotein I Antibody (b2GPI)
(June 2007)
(Download 
Anti-beta2-Glycoprotein.pdf)
Background - What is the antiphospholipid antibody syndrome?
Antiphospholipid antibody syndrome (APS) is present if at least one of the clinical criteria and one of the laboratory criteria that follow are met
Clinical criteria
1. Vascular thrombosis
- One or more clinical episodes of arterial, venous, or small vessel thrombosis, in any tissue or organ.
2. Pregnancy morbidity
- One or more unexplained deaths of a morphologically normal fetus at or beyond the 10th week of gestation, or
- One or more premature births of a morphologically normal neonate before the 34th week of gestation because of eclampsia or placental insufficiency, or
- Three or more unexplained consecutive spontaneous abortions before the 10th week of gestation.
Laboratory criteria
- Lupus anticoagulant (LA) present in plasma, on two or more occasions at least 12 weeks apart.
- Anticardiolipin (aCL) antibody, present in medium or high titer (i.e. >40 GPL or MPL), on two or more occasions, at least 12 weeks apart.
- Anti-b2 glycoprotein-I antibody, present on two or more occasions, at least 12 weeks apart.
Who should be tested?
Any patient with features of antiphospholipid antibody syndrome (APS, see below).
What does the result mean?
A positive anti-b2GPI is very specific for APS.
To improve sensitivity and to aid interpretation of results HAPS recommends testing anti-b2GPI in addition to anticardiolipin antibody (aCL) and lupus inhibitor (also called Lupus Anticoagulant, LA).
Although any patient with a thrombotic event is therefore at higher risk than the population for further such events, this risk is higher still in those with APS. APS testing is one factor that most clinicians would include in the decision of risk vs. benefit in regards to type and duration of anticoagulation. Patients with obstetric complications are similarly at risk of further events, and this is more likely in those with APS. Women with recurrent foetal loss and APS may benefit from heparin, and possibly aspirin, therapy.
What does anti-b2GPI testing add to cardiolipin antibody and lupus inhibitor testing?
HAPS still recommends testing for aCL and LA, either of which are positive in most patients with APS. LA and aCL can also be present in patients without APS and/or thrombosis, with reported specificity of LA for APS of 79% and lower for aCL.
A positive anti-b2GPI increases the likelihood that the patient has APS. One series reported that patients with both LA and b2GPI antibodies had an Odds Ratio of 4.0 for thrombosis when compared to those with LA alone.
Testing with anti-b2GPI antibody instead of either LA or aCL is not recommended as anti-b2GPI alone is less sensitive that the combination of LA and aCL, potentially missing patients with APS. Patients with b2GPI without aCL are reported, but rare.
Immunology Contacts
Dr Glenn Reeves / Dr Theo de Malmanche (Clinical Staff Specialists) – 49214018
Prof Robert Clancy (Director/Clinical staff specialist) – 49214018
Immunology Laboratory - 49214018