GBM Ab, IgG, Muliplex Bead Assay and IFA
Test Mnemonic
GBMGP
CPT Codes
- 83516 - QTY (1)
- 86255 - QTY (1)
Performing Laboratory
ARUP
FDA Category
Laboratory Developed Test
Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 1 mL | Serum | SST (Gold) | Refrigerated | Separate serum from cells ASAP or within 2 hours of collection |
Minimum Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 0.3 mL |
Stability
| Environmental Condition | Description |
|---|---|
| Ambient | After separation from cells: 2 days |
| Frozen | After separation from cells: 1 year (avoid freeze/thaw cycles) |
| Refrigerated | After separation from cells: 2 weeks |
Days Performed
Mon - Fri
Turnaround Time
2 - 6 days
Methodology
| Name | Description |
|---|---|
| Indirect Fluorescent Antibody (IFA) | |
| Multiplex Bead Assay |
Reference Range
| GBM Ab, IgG (Bead) | |||||
|---|---|---|---|---|---|
| Sex | Age From | Age To | Type | Range | Range Unit |
| Years | 99 Years | Normal | Negative: <=19 | AU/mL | Years | 99 Years | Normal | Equivocal: 20 - 25 | AU/mL | Years | 99 Years | Normal | Positive: >=26 | AU/mL |
Special Info
Separate serum from cells ASAP or within 2 hours of collection.
Clinical Info
GBM IgG IFA: The anti-GBM IFA methodology has been shown to be less specific than the semi-quantitative tests for circulating antibodies. The antibody used in the Multiplex Bead Assay, although directed to human IgG F (ab')2, can bind to light chain sites common to all immunoglobulins, causing the assay to be more sensitive but less specific. The determination of a positive result is based on a diffuse "linear" staining pattern as viewed through a fluorescent microscope. All positive results should be confirmed by semi-quantitative tests and/or renal biopsy. GBM IgG Muliplex Bead Assay: The presence of anti-glomerular basement membrane (GBM) antibodies by Muliplex Bead assay may aid in the diagnosis of Goodpasture syndrome. False positive results may occur due to reactivity against other chains of type IV collagen. If Multiplex Bead Assay is negative but there is strong suspicion for disease, renal biopsy may be indicated. A renal biopsy may also be essential in suspected Goodpasture disease with renal involvement, allowing diagnostic confirmation and assessment of renal prognosis.