Beta-2 Glycoprotein 1 Antibodies, IgA, Serum
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Evaluation of suspected cases of antiphospholipid syndrome
Enzyme-Linked Immunosorbent Assay (ELISA)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Beta 2 GP1 Ab IgA, S
B2GP1 (Beta-2 Glycoprotein 1)
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Preferred: Red top
Acceptable: Serum gel
Specimen Volume: 0.5 mL
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Mild OK; Gross reject
Mild OK; Gross reject
Mild OK; Gross OK
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
|Serum||Refrigerated (preferred)||21 days|
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
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 anti-phospholipid 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 antibodies 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.(5) 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 presence of lupus anticoagulant, presence of IgG and/or IgM anticardiolipin antibody (>40 GPL, >40 MPL or >99th percentile), and/or presence of IgG and/or IgM beta 2 GP1 antibody (>99th percentile). All antibodies must be demonstrated on 2 or more occasions separated by at least 12 weeks. Direct assays for beta 2GP 1 antibodies have been reported to be somewhat more specific (but less sensitive) for disease diagnosis in patients with APS.(4) Anti-cardiolipin and beta 2 GP1 antibodies of the IgA isotype are not part of the laboratory criteria for APS due to lack of specificity.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
<10.0 U/mL (negative)
10.0-14.9 U/mL (borderline)
> or =15.0 U/mL (positive)
Results are expressed in arbitrary units.
Reference values apply to all ages.
Strongly positive results for IgG and IgM beta 2 GP1 antibodies (>40 U/mL for IgG and/or IgM) are diagnostic criterion for antiphospholipid syndrome (APS). Lesser levels of 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.
IgA beta 2 GP1 antibody result >15 U/mL with negative IgG and IgM beta 2 GP1 antibody results are not diagnostic for APS.
Detection of beta 2 GP1 antibodies is not affected by anticoagulant treatment.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
The immunoassay for beta 2 GP1 antibodies does not distinguish between autoantibodies and antibodies produced in response to infectious agents or as epiphenomena following thrombosis. For this reason, a single positive test result is not sufficient to meet accepted serologic criteria for the diagnosis of antiphospholipid syndrome (see above).
Comparative studies and interlaboratory proficiency surveys indicate that results of beta 2 GP1 antibody tests can be highly variable and results obtained with different commercial immunoassays may yield substantially different results.(5)
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
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. 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
5. 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
Method Description Describes how the test is performed and provides a method-specific reference
This indirect, noncompetitive enzyme-linked immunosorbent assay (ELISA) uses microtiter plates coated with purified, human beta 2 GP1. Beta 2 GP1 antibodies bound in the first stage of the assay are detected with antihuman IgA horseradish peroxidase antibody conjugate in the second stage of the assay by adding 3,3',5,5' tetramethylbenzidine substrate (10 minute incubation followed by addition of 0.5 M HSO). The absorbance of test sera is compared to a single cutoff calibrator. Results for test sera are expressed in arbitrary U/mL by comparison with standard curves obtained using calibrators at 0, 4, 8, 20, 50, and 100 U/mL. (Package insert: Varelisa Beta 2 Glycoprotein 1 IgM, Antibodies, doc 189-01, Phadia Diagnostics, Portage, MI)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Saturday; 8 a.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Same day/1 day
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
This test has been cleared or approved by the U.S. 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 Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
|Result ID||Reporting Name||LOINC Code|
|AB2GP||Beta 2 GP1 Ab IgA, S||44447-1|