ANCA

The expected result is Negative. A positive is reported with a pattern, cANCA or pANCA, and is usually followed by measurement of the two specific antibodies, PR3 and MPO, which are reported separately with their own numbers.

ANCA are antibodies directed against substances inside neutrophils, the commonest type of white blood cell. The laboratory looks for them by adding blood to neutrophils on a slide and watching the pattern of glow under a fluorescent microscope: cANCA when the glow is spread through the cell, pANCA when it sits around the nucleus. They are linked with a group of conditions in which small blood vessels become inflamed (vasculitis).

Doctors request it when looking at vasculitis, particularly when someone has unexplained kidney inflammation, blood in the urine, nosebleeds, sinus problems, lung shadows or a rash that does not fade. It is also sometimes positive in inflammatory bowel disease and some liver conditions.

• ANCA-associated vasculitis, including granulomatosis with polyangiitis and microscopic polyangiitis
• Ulcerative colitis and some liver conditions such as primary sclerosing cholangitis, usually pANCA
• Some long-term infections, including infective endocarditis
• Some medicines, including some thyroid medicines and hydralazine
• Some other autoimmune conditions, at low levels

• Negative is the usual finding in healthy adults
• Treatment of vasculitis with immune-suppressing medicines
• Quieter periods of the condition

• A weak pANCA pattern is found in a small number of healthy adults and in a range of conditions unrelated to vasculitis
• Methods differ between laboratories, and a weak positive on one method may be negative on another
• Some other antibodies, including antinuclear antibodies, can give a false pANCA pattern on the slide

No fasting needed. A single result is read alongside the PR3 and MPO antibody levels that usually follow it; in people with a known vasculitis those numbers, rather than the screen, are followed over time.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.