Anti-glomerular basement membrane antibody

This blood test looks for antibodies that target the glomerular basement membrane, a thin structure in your kidneys that helps filter waste. These antibodies are usually of the IgG type and are measured by immunoassays.

Finding these antibodies supports the diagnosis of anti-GBM disease, also called Goodpasture disease, which can affect the kidneys and sometimes the lungs. The test can also be used to follow how you respond to treatment over time.

Anti-GBM disease can injure the kidneys quickly, so timely testing helps your care team confirm the cause of sudden kidney inflammation or bleeding in the lungs. Your clinician may order this test if you have blood in the urine, a rapid drop in kidney function, coughing up blood, or imaging that suggests lung bleeding, often alongside other autoimmune tests.

Your results help guide urgent treatments, such as immunosuppressive medicines and plasma exchange, and help distinguish anti-GBM disease from other causes of glomerulonephritis when combined with a kidney biopsy and other lab findings.

A positive result means your immune system is making antibodies that target the kidney’s basement membrane, which is consistent with anti-GBM disease. Your clinician will interpret this result together with your symptoms, urine tests, kidney function, and sometimes a kidney biopsy or lung imaging.

A negative result does not always rule out disease, especially very early in illness or after treatments that lower antibody levels. If clinical suspicion remains high, your clinician may repeat the test or use a different method. Rarely, other autoimmune conditions can produce weak positives, so confirmation may be needed.

If you are receiving treatment, decreasing antibody levels usually suggest improvement, while rising levels may prompt closer monitoring or changes in therapy. Seek urgent care if you develop coughing up blood or a sudden drop in urine output.