What is the anti-glomerular basement membrane test?

The anti-glomerular basement membrane (anti-GBM) test looks for anti-glomerular basement membrane antibodies that attack a part of the kidney known as the glomerular basement membrane (GBM). Anti-GBM antibodies are associated with kidney damage.

Anti-GBM antibodies attack capillaries in the GBM. These attacks cause problems with kidney function. These problems can lead to blood and blood proteins leaking into your urine.

Anti-GBM antibodies also can attack the basement membranes in your lungs. As a result, the air sacs in your lungs can become filled with blood and proteins. This can cause lung damage and difficulty breathing.

The anti-GBM test can help your doctor diagnose diseases that affect the kidneys and lungs, known as anti-GBM diseases.

When disease only affects the kidneys, it’s known as anti-GBM glomerulonephritis. Goodpasture syndrome is when it affects both the kidneys and the lungs. According to Vasculitis UK, anti-GBM diseases cause inflammation of the blood vessels in the kidneys and lungs. It tends to affect men more than women. It also usually appears in people in their 20s and those in their 60s and 70s.

The following may be symptoms of both anti-GBM glomerulonephritis and Goodpasture syndrome:

  • weight loss
  • fatigue
  • chills and fever
  • coughing up blood
  • nausea and vomiting
  • chest pain
  • anemia caused by bleeding
  • respiratory failure
  • kidney failure

You don’t need to make any specific preparations before having an anti-GBM test. The anti-GBM test only requires a blood sample.

To draw blood, your doctor will wrap an elastic band around your upper arm. This stops blood flow and makes veins in your arm more visible. Seeing the veins makes it easier to insert a needle.

After locating a vein, your doctor will clean the skin around the vein with alcohol. Then they will insert a needle into your vein. A tube attached to the end of the needle will collect the blood.

After collecting enough blood, your doctor will remove the elastic band from your arm. After removing the needle, they’ll place cotton or gauze on the injection site and secure it with a bandage.

There are few risks involved with having blood drawn. Some bruising may appear at the needle site. You can lessen bruising by applying pressure to the area for several minutes after the needle is removed.

In rare cases, having blood drawn has the following risks:

  • fainting or lightheadedness
  • excessive bleeding
  • hematoma (an accumulation of blood beneath the skin)
  • infection

Normal results

Researchers have found that you have less than a 10 percent chance of having anti-GBM disease or Goodpasture syndrome if no anti-GBM antibodies are detected in the blood.

Even if the results of your test are normal, your doctor may still suspect you have one of the conditions. If so, your doctor may order a lung or kidney biopsy.

Abnormal results

If the test found anti-GBM antibodies in your blood, there is a 95 to 100 percent chance you have anti-GBM disease or Goodpasture syndrome. Your doctor may ask you to undergo more tests to confirm a diagnosis, including a lung or kidney biopsy.

Your doctor will determine your exact diagnosis after reviewing your test results and symptoms. There are several treatments available for both anti-GBM disease and Goodpasture syndrome.

One treatment is plasmapheresis. This treatment involves taking blood out of the body and removing the antibodies. This process uses a machine to remove the antibodies. If you have this treatment, you’ll need to undergo the process daily for two weeks, according to Vasculitis UK.

Another treatment is immunosuppression with methylprednisolone. This treatment prevents the production of more antibodies.

Depending on your case, you may be able to recover. But if you have extensive kidney damage, you may need to undergo treatment like dialysis.

Treatments for anti-GBM diseases are powerful and can sometimes lead to infection. Pulmonary infections will occur either as a result of lung damage or immunosuppression from treatment. Proper surveillance and early treatment of infection can lessen complications.

There are also side effects of steroid or other immunosuppressive treatment including UTIs, skin infections, or sepsis. Other side effects might include gastritis and peptic ulcer disease, and osteoporosis.

You can help your recovery by looking out for symptoms of infection, taking medication exactly as prescribed, and ingesting enough fluids.