This test looks for antineutrophil cytoplasmic antibodies (ANCA) in your blood. Antibodies are proteins that your immune system makes to fight foreign substances like viruses and bacteria. But ANCAs attack healthy cells known as neutrophils (a type of white blood cell) by mistake. This can lead to a disorder known as autoimmune vasculitis. Autoimmune vasculitis causes inflammation and swelling of the blood vessels.

Blood vessels carry blood from your heart to your organs, tissues, and other systems, and then back again. Types of blood vessels include arteries, veins, and capillaries. Inflammation in the blood vessels can cause serious health problems. Problems vary depending on which blood vessels and body systems are affected.

There are two main kinds of ANCA. Each targets a specific protein inside white blood cells:

- pANCA, which targets a protein called MPO (myeloperoxidase)
- cANCA, which targets a protein called PR3 (proteinase 3)

The test can show whether you have one or both types of antibodies. This can help your health care provider diagnose and treat your disorder.

An ANCA test is most often used to find out if you have a type of autoimmune vasculitis. There are different types of this disorder. They all cause inflammation and swelling of blood vessels, but each type affects different blood vessels and parts of the body. 

Types of autoimmune vasculitis include:

Granulomatosis with polyangiitis (GPA), previously called Wegener's disease. It most often affects the lungs, kidneys, and sinuses.
Microscopic polyangiitis (MPA). This disorder can affect several organs in the body, including the lungs, kidneys, nervous system, and skin.

Eosinophilic granulomatosis with polyangiitis (EGPA), previously called Churg-Strauss syndrome. This disorder usually affects the skin and lungs. It often causes asthma.

Polyarteritis nodosa (PAN). This disorder most often affects the heart, kidneys, skin, and central nervous system.
An ANCA test may also be used to monitor treatment of these disorders.

Possible symptoms of autoimmune vasculitis include:

- Fever
- Fatigue
- Weight loss
- Muscle and/or joint aches

Your symptoms may also affect one or more specific organs in your body. Commonly affected organs and the symptoms they cause include:

- Eyes
- Redness
- Blurred vision
- Loss of vision
- Ears
- Ringing in the ears (tinnitus)
- Hearing loss
- Sinuses
- Sinus pain
- Runny nose
- Nose bleeds
- Skin
- Rashes
- Sores or ulcers, a type of deep sore that's slow to heal and/or keeps coming back
- Lungs
- Cough
- Trouble breathing
- Chest pain
- Kidneys
- Blood in the urine
- Foamy urine, which is caused by protein in the urine
- Nervous system
- Numbness and tingling in different parts of the body