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HelpTest Code AGBM Glomerular Basement Membrane Antibodies, IgG, Serum
Additional Codes
| Mayo Test ID |
|---|
| GBM |
Reporting Name
Glomerular Basement Membrane IgG AbUseful For
Evaluating patients with clinical features of anti-glomerular basement disease, including rapidly progressive glomerulonephritis or pulmonary hemorrhage
Method Name
Multiplex Flow Immunoassay
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
SerumOrdering Guidance
If patient is being evaluated for autoimmune skin disease, order CIFS / Cutaneous Immunofluorescence Antibodies (IgG), Serum for evaluation of anti-intercellular substance (ICS) and antibasement membrane zone (BMZ) antibodies.
Specimen Required
Supplies: Sarstedt Aliquot Tube 5 mL (T914)
Collection Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 0.5 mL
Collection Instructions: Centrifuge and aliquot serum into a plastic vial.
Specimen Minimum Volume
0.35 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Refrigerated (preferred) | 21 days | |
| Frozen | 21 days |
Reject Due To
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
| Gross icterus | OK |
Reference Values
<1.0 U (negative)
≥1.0 U (positive)
Reference values apply to all ages.
Day(s) Performed
Monday through Friday
CPT Code Information
83516
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| GBM | Glomerular Basement Membrane IgG Ab | 31254-6 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| GBM | Glomerular Basement Membrane IgG Ab | 31254-6 |
Clinical Information
Anti-glomerular basement (GBM) disease is a rare autoimmune disease, with an estimated incidence of 0.6-1.79 cases per million population per year.(1) Without prompt treatment, this disease is potentially fatal. Patients may present with rapidly progressive glomerulonephritis, pulmonary hemorrhage, or both.(2,3) The serological hallmark of this disease is the presence of anti-GBM antibodies of the IgG isotype. Anti-GBM antibodies bind to the non-collagenous domain 1 (NC1) of the alpha3 chain of type IV collagen, which is one of the main components of the kidney and lung basement membranes. Deposition of anti-GBM antibodies in the kidney and lungs triggers complement activation and production of reactive oxygen species, ultimately leading to vascular necrosis and damage to the GBM.
The diagnosis of anti-GBM disease in a patient with compatible clinical symptoms is often confirmed by detecting the presence of anti-GBM antibodies. This can be accomplished by a variety of antigen-specific, solid-phase immunoassays. Given the implications of this testing, understanding the diagnostic sensitivity and specificity of anti-GBM antibody methods is critical. In a recent meta-analysis, a pooled sensitivity of 93% (95%CI: 84-97%) and a pooled specificity of 97% (95%CI: 94-99%) was demonstrated across 11 methods.(4) In addition, some studies have suggested a prognostic role for anti-GBM antibodies, with higher titers being associated with increased mortality. However, it appears that this effect can largely be abrogated by prompt and aggressive treatment, particularly plasmapheresis.(1)
Interpretation
A positive result for anti-glomerular basement (GBM) antibody is consistent with the diagnosis of anti-GBM disease, in patients with the appropriate clinical presentation.
Cautions
A positive result for anti-glomerular basement (GBM) antibodies is not diagnostic for anti-GBM disease and must be interpreted in the clinical context of the patient.
A negative result for anti-GBM antibodies does not exclude the possibility of anti-GBM disease, particularly in patients treated with immunosuppressants or plasmapheresis prior to testing.
Method Description
Glomerular basement membrane (GBM) antigen is covalently coupled to polystyrene microspheres that are impregnated with fluorescent dyes to create a unique fluorescent signature. GBM antibodies, if present in diluted serum, bind to the GBM antigen on the microspheres. The microspheres are washed to remove extraneous serum proteins. Phycoerythrin (PE)-conjugated antihuman-IgG antibody is then added to detect IgG anti-GBM bound to the microspheres. The microspheres are washed to remove unbound conjugate, and bound conjugate is detected by laser photometry. A primary laser reveals the fluorescent signature of each microsphere to distinguish it from microspheres that are labeled with other antigens. A secondary laser reveals the level of PE fluorescence associated with each microsphere. Results are calculated by comparing the median fluorescence response for GBM microspheres to a 4-point calibration curve.(Package insert: Bio-Plex 2200 Vasculitis. Bio-Rad Laboratories; 12/2018)