What this test measures
This test detects IgG antibodies directed against the non-collagenous (NC1) domain of type IV collagen — a structural protein in the basement membrane of kidney glomeruli and lung alveoli. The antibodies bind to and damage these membranes, causing rapidly progressive glomerulonephritis (kidney failure) and/or alveolar haemorrhage (lung bleeding).
The assay is usually a quantitative ELISA against the alpha-3 chain of type IV collagen. Results are reported in EU/mL or U/mL; positivity is highly specific for anti-GBM disease (also called Goodpasture syndrome when both kidneys and lungs are involved).
Why it matters
Anti-GBM disease is rare (about 1 case per million people per year) but it is a medical emergency. Untreated, patients can lose kidney function within days to weeks and die from massive lung bleeding. Survival and kidney recovery depend almost entirely on how quickly the diagnosis is made and treatment (plasma exchange, immunosuppression, steroids) is started.
This test is ordered whenever someone presents with rapidly worsening kidney function (rising creatinine over days), blood and protein in the urine, or unexplained alveolar haemorrhage (coughing blood, breathlessness, anemia). In India, anti-GBM is often considered alongside ANCA testing in patients presenting with pulmonary-renal syndrome — both conditions can look similar at presentation and require very different long-term treatment. About 10–15% of anti-GBM patients are also ANCA-positive ("double-positive") and have a slightly different disease course.
How to prepare
No fasting required. Take all your usual medications. If you are already on immunosuppression or plasma exchange for suspected anti-GBM disease, the level may be lower than at initial presentation — note these treatments to your doctor.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Anti-GBM IgG (U/mL or EU/mL)[1][2][3] | Negative: < 7 (assay-dependent) | Negative result makes anti-GBM disease unlikely. In a few patients early in disease the ELISA can be falsely negative — if clinical suspicion is high (rapid kidney decline + lung bleeding), a kidney biopsy with linear IgG staining on immunofluorescence is the gold standard. | Positive anti-GBM IgG is highly specific for anti-GBM disease (Goodpasture syndrome when lungs are also involved). Higher titres correlate with more aggressive kidney injury. Treat as a medical emergency — refer to nephrology for plasma exchange, cyclophosphamide, and high-dose steroids without delay. |
Pulmonary-renal syndrome: anti-GBM vs ANCA vasculitis
| Feature | Anti-GBM Disease | ANCA Vasculitis (GPA/MPA) |
|---|---|---|
| Typical age | 20s–30s or 60s–70s (bimodal) | 50s–70s |
| Kidney involvement | Almost always, rapid | Common, sometimes subacute |
| Lung involvement | ~50% (alveolar haemorrhage) | ~50% (haemorrhage or nodules) |
| Sinus / ENT disease | Not typical | Common in GPA |
| Diagnostic antibody | Anti-GBM IgG | PR3-ANCA (c-ANCA) or MPO-ANCA (p-ANCA) |
| Biopsy pattern | Linear IgG deposition | Pauci-immune (no immune deposits) |
| First-line treatment | Plasma exchange + cyclophosphamide + steroids | Cyclophosphamide or rituximab + steroids |
| Relapse risk | Low (often single episode) | Moderate to high |
Frequently asked questions
Why has my doctor ordered this test?
Usually because of rapidly rising creatinine, blood and protein in the urine, or unexplained lung bleeding — symptoms that suggest anti-GBM disease. The test is rarely done as routine screening.
How fast do results come back?
Most labs report anti-GBM within 24–48 hours. If clinical suspicion is high, doctors may start treatment empirically while awaiting the result.
Is anti-GBM disease curable?
With prompt treatment, the antibody can usually be cleared and the disease often does not recur. However, kidney damage already present at diagnosis may not reverse — many patients with severe presentation end up on dialysis. Early diagnosis is critical.
Can the test be falsely positive?
Modern ELISA assays are highly specific. Borderline values are sometimes confirmed by a second method or by kidney biopsy with immunofluorescence.
Will I need a kidney biopsy?
Usually yes — a biopsy showing linear IgG staining along the basement membrane confirms the diagnosis and rules out overlapping conditions like ANCA vasculitis.
Is this test also done after a kidney transplant?
Yes. Patients who had anti-GBM disease before transplant are checked to make sure antibody levels have stayed negative for at least 6 months, because transplanting into an antibody-positive recipient causes immediate graft loss.
Related Autoimmune / Rheumatology tests
Tests commonly ordered alongside ANTI GLOMERULAR BASEMENT MEMBRANE PROTEIN - IgG, or that help interpret an unexpected result.
Sources & references
- NIH MedlinePlus — Anti-Glomerular Basement Membrane Test · accessed 2026-05-30T00:00:00.000Z
- NCBI StatPearls — Goodpasture Syndrome · accessed 2026-05-30T00:00:00.000Z
- KDIGO — Glomerulonephritis Clinical Practice Guideline · accessed 2026-05-30T00:00:00.000Z
- Mayo Clinic Labs — Glomerular Basement Membrane Antibody · accessed 2026-05-30T00:00:00.000Z
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