An ANCA by IFA reflex MPO/PR3 serum diagnostic test is a highly specific method used for diagnosing and monitoring ANCA-associated vasculitis (AAV), a rare group of autoimmune diseases that affect small to medium blood vessels.

The test begins with an indirect immunofluorescence assay (IFA) on human serum. This initial step determines the presence of antineutrophil cytoplasmic antibodies (ANCA) and characterizes their staining pattern, typically as either cytoplasmic (c-ANCA) or perinuclear (p-ANCA). If the IFA test yields a positive result, a reflex test is automatically performed. This reflex step uses enzyme-linked immunosorbent assay (ELISA) technology to precisely measure the concentration of antibodies specific for myeloperoxidase (MPO) and proteinase 3 (PR3).

This combined diagnostic approach provides comprehensive data, enabling healthcare providers to accurately identify the specific ANCA-associated vasculitis type, such as granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), or eosinophilic granulomatosis with polyangiitis (EGPA), and initiate appropriate treatment strategies.