Antineutrophil cytoplasmic antibodies (ANCA) are autoantibodies produced by a person’s immune system. ANCA testing detects and measures the amount of these autoantibodies in the blood. Two of the most common types or subsets of ANCA are the autoantibodies that target the proteins myeloperoxidase (MPO) and proteinase 3 (PR3).
The normal test result should be negative.
Positive ANCA, PR3, and/or MPO tests help to support a diagnosis of systemic autoimmune vasculitis and to distinguish between different types. However, to confirm a diagnosis, a biopsy of an affected site is often required.
Negative ANCA tests results mean it is unlikely that a person’s symptoms are due to an autoimmune vasculitis.
ANCA testing can be useful in evaluating patients with symptoms of an inflammatory bowel disease (IBD).
If atypical ANCA is positive and ASCA (anti-Saccharomyces cerevisiae antibodies) is negative, then it is likely that the person has ulcerative colitis (UC).
If atypical ANCA is negative and ASCA is positive, then it is likely that the person has Crohn disease (CD). A person who is negative for ANCA and/or ASCA may still have UC, CD, or another IBD.