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Test ID GB2GP Beta-2 Glycoprotein 1 Antibodies, IgG, Serum

Reporting Name

Beta 2 GP1 Ab IgG, S

Useful For

Evaluation of patients with suspected antiphospholipid syndrome by identification of beta-2 GP1 IgG antibodies

Specimen Type


Specimen Required


Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 0.5 mL

Specimen Minimum Volume

0.4 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 21 days
  Frozen  21 days

Reference Values

<15.0 U/mL (negative)

15.0-39.9 U/mL (weakly positive)

40.0-79.9 U/mL (positive)

≥80.0 U/mL (strongly positive)

Results are expressed in arbitrary units.

Reference values apply to all ages.

Day(s) Performed

Monday through Saturday

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
GB2GP Beta 2 GP1 Ab IgG, S 44448-9


Result ID Test Result Name Result LOINC Value
GB2GP Beta 2 GP1 Ab IgG, S 44448-9

Clinical Information

Beta-2 glycoprotein 1 (beta-2 GP1, also called apolipoprotein H) is a 326-amino acid polypeptide synthesized by hepatocytes, endothelial cells, and trophoblast cells. It contains 5 homologous domains of approximately 60 amino acids each.(1,2) Domain 5, located at the C terminus, contains a hydrophobic core surrounded by 14 positively charged amino acid residues that promote electrostatic interactions with plasma membranes via interactions with negatively charged phospholipids. Complexes of beta 2 GP1 and phospholipid in vivo reveal epitopes that react with natural autoantibodies.(3) Plasma from normal individuals contains low concentrations of IgG autoantibodies to beta-2 GP1 (beta-2 GP1 antibodies) that are of moderate affinity and react with an epitope on the first domain near the N terminus.


Pathologic levels of beta 2 GP1 antibodies occur in patients with antiphospholipid syndrome (APS). APS is associated with a variety of clinical symptoms notably thrombosis, pregnancy complications, unexplained cutaneous circulatory disturbances (livido reticularis or pyoderma gangrenosum), thrombocytopenia or hemolytic anemia, and nonbacterial thrombotic endocarditis. Beta 2 GP1 antibodies are found with increased frequency in patients with systemic rheumatic diseases, especially systemic lupus erythematosus.


Autoantibodies to beta-2 GP1 are detected in the clinical laboratory by different types of assays including immunoassays and functional coagulation assays. Immunoassays for beta-2 GP1 antibodies can be performed using either a composite substrate comprised of beta-2 GP1 plus anionic phospholipid (eg, cardiolipin or phosphatidylserine), or beta-2 GP1 alone. Antibodies detected by immunoassays that utilize composite substrates are commonly referred to as phospholipid or cardiolipin antibodies. Antibodies detected using beta-2 GP1 substrate without phospholipid (so-called direct assays) are referred to simply as "beta-2 GP1 antibodies." Some beta-2 GP1 antibodies are capable of inhibiting clot formation in functional coagulation assays that contain low concentrations of phospholipid cofactors. Antibodies detected by functional coagulation assays are commonly referred to as lupus anticoagulants.


The diagnosis of APS requires at least 1 clinical criteria and 1 laboratory criteria be met.(4) The clinical criteria include vascular thrombosis (arterial or venous in any organ or tissue) and pregnancy morbidity (unexplained fetal death, premature birth, severe preeclampsia, or placental insufficiency). Other clinical manifestations, including heart valve disease, livedo reticularis, thrombocytopenia, nephropathy, neurological symptoms, are often associated with APS but are not included in the diagnostic criteria. The laboratory criteria for diagnosis of APS are the presence of lupus anticoagulant, the presence of IgG and/or IgM anticardiolipin antibody (>40 GPL, >MPL, or >99th percentile), and/or the presence of IgG and/or IgM beta GP1 antibody (>99th percentile). All antibodies must be demonstrated on 2 or more occasions separated by at least 12 weeks. Direct assays for beta-2 GP1 antibodies have been reported to be somewhat more specific (but less sensitive) for disease diagnosis in patients with APS.(5) Anticardiolipin and beta-2 GP1 antibodies of the IgA isotype are not part of the laboratory criteria for APS due to lack of specificity.


Strongly positive results for beta 2 glycoprotein 1 (beta 2 GP1) antibodies (>40 U/mL for IgG and/or IgM) are diagnostic criterion for antiphospholipid syndrome (APS). Lesser levels of IgG and IgM beta 2 GP1 antibodies and antibodies of the IgA isotype may occur in patients with clinical signs of APS, but the results are not considered diagnostic. Beta 2 GP1 antibodies must be detected on 2 or more occasions at least 12 weeks apart to fulfill the laboratory diagnostic criteria for APS.


Detection of beta 2 GP1 antibodies is not affected by anticoagulant treatment.

Clinical Reference

1. Caronti B, Calderaro C, Alessandri C, et al: Beta 2 glycoprotein 1 (beta 2 GP1) mRNA is expressed by several cell types involved in anti-phospholipid syndrome-related tissue damage. Clin Exp Immunol 1999;115:214-219

2. Lozier J, Takahashi N, Putnam F: Complete amino acid sequence of human plasma beta 2 glycoprotein 1. Proc Natl Acad Sci USA 1984;81:3640-3644

3. Kra-Oz Z, Lorber M, Shoenfeld Y, Scharff Y: Inhibitor(s) of natural anti-cardiolipin autoantibodies. Clin Exp Immunol 1993;93:265-268

4. Wong RCW, Flavaloro EJ, Adelstein S, et al: Consensus guidelines on anti-beta 2 glycoprotein I testing and reporting. Pathology 2008 Jan;40(1):58-63

5. Audrain Ma, El-Kouri D, Hamidou MA, et al: Value of autoantibodies to beta(2)-glycoprotein 1 in the diagnosis of antiphospholipid syndrome. Rheumatology (Oxford) 2002;41:550-553

Report Available

Same day/1 to 6 days

Method Name

Enzyme-Linked Immunosorbent Assay (ELISA)