ANCA (Anti-Neutrophil Cytoplasmic Antibodies)

What is being tested?

Antineutrophil cytoplasmic antibodies (ANCA) are autoantibodies generated by the immune system, which erroneously direct their attack towards specific proteins found within neutrophils, a type of white blood cell. ANCA testing serves to identify and quantify the presence of these autoantibodies in the bloodstream. Among the most prevalent ANCAs, two types are often encountered: pANCAs, which target myeloperoxidase (MPO) proteins, and cANCAs, which target proteinase 3 (PR3) proteins.

What is the purpose of the test?

Tests for antineutrophil cytoplasmic antibodies (ANCA) may serve the following purposes:

1. Aid in the detection and diagnosis of specific autoimmune vasculitis conditions, including granulomatosis with polyangiitis (Wegener granulomatosis), microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome). Occasionally, these tests may also be employed to monitor treatment progress and identify potential relapses in these conditions.
2. Assist in distinguishing between ulcerative colitis (UC) and Crohn's disease (CD), which are two prevalent forms of inflammatory bowel disease (IBD).
3. The testing approach can vary, with some laboratories conducting all three tests (ANCA, MPO, and PR3) as a panel, while others perform MPO and PR3 tests only when the initial ANCA test yields a positive result.

When is the ANCA test recommended?

An ANCA test and/or tests for MPO and PR3 are typically ordered when you exhibit signs and symptoms suggestive of systemic autoimmune vasculitis. In the early stages of the disease, these symptoms can be vague or nonspecific and may include fever, fatigue, weight loss, muscle and/or joint aches, and night sweats. As the condition progresses, damage to blood vessels throughout the body can lead to various signs and symptoms related to complications affecting different tissues and organs. Some examples of these manifestations include:

• Eyes: Red, itchy eyes or "pink eye" (conjunctivitis); visual problems like blurry vision or loss of vision.
• Ears: Hearing loss.
• Nose: Persistent upper respiratory symptoms, such as a runny nose, that do not resolve.
• Skin: Rashes and/or granulomas.
• Lungs: Coughing and/or breathing difficulties.
• Kidneys: Presence of protein in the urine.

Periodic testing may also be conducted while you are undergoing treatment for autoimmune vasculitis to monitor your condition's progression and response to therapy.

What does the test result show?

The results of ANCA tests require careful interpretation, considering several factors. Your healthcare provider will evaluate your signs and symptoms in conjunction with the laboratory test results and other diagnostic assessments, such as imaging studies.

in the majority of cases, a biopsy of a blood vessel affected by the condition is required to definitively confirm a diagnosis of autoimmune vasculitis.

What are additional tests besides ANCA?

Additional diagnostic tests that might be conducted to assist in the diagnosis include assessing erythrocyte sedimentation rate (ESR) and/or C-reactive protein (CRP) levels to determine inflammation, conducting a complete blood count (CBC) to measure and assess white and red blood cells, and performing urinalysis, blood urea nitrogen (BUN), and creatinine tests to evaluate kidney function. In certain cases, viral tests for infections like hepatitis or cytomegalovirus may also be recommended.

Are there any other disorders that can cause a positive ANCA?

Yes. Rheumatoid arthritis, systemic lupus erythematosus (SLE), lung conditions, autoimmune hepatitis, use of certain drugs, and infections involving the heart (endocarditis) or the respiratory system are some conditions.