c-ANCA Blood Test (Antineutrophil Cytoplasmic Antibody)

The c-ANCA blood test detects a specific autoantibody that targets proteins within neutrophil cytoplasm. It is used to support the diagnosis and monitoring of certain small-vessel vasculitides, most notably granulomatosis with polyangiitis (GPA, formerly Wegener's granulomatosis), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). It is also helpful in distinguishing these conditions from other inflammatory or infectious diseases that can present with similar symptoms.

This test is typically requested for patients with unexplained persistent sinusitis, nosebleeds, chronic ear infections, cough, breathlessness, haemoptysis, kidney inflammation, skin rashes, or peripheral neuropathy. It may also be used to track disease activity and guide treatment decisions in patients with a known diagnosis.

Autoantibodies
- c-ANCA (cytoplasmic antineutrophil cytoplasmic antibody): Detects antibodies directed against proteinase 3 (PR3), which are strongly associated with GPA. A positive result, when combined with clinical findings, supports the diagnosis of ANCA-associated vasculitis and can help predict the likelihood of renal involvement.

Why it matters
ANCA-associated vasculitides can cause rapid, irreversible organ damage if left untreated. Early detection of c-ANCA allows clinicians to initiate appropriate immunosuppressive therapy promptly, monitor response to treatment, and identify relapses before significant organ injury occurs. This test provides essential information for a timely and accurate diagnosis, guiding specialist care and improving long-term outcomes.