Description

ANCA (antineutrophil cytoplasmic antibodies) are a group of autoantibodies that target proteins found in the cytoplasm of neutrophils (a type of white blood cell). These antibodies are associated with several autoimmune diseases, particularly small vessel vasculitis, including granulomatosis with polyangiitis (GPA, formerly known as Wegener’s granulomatosis), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA, formerly known as Churg-Strauss syndrome).

The term “ANCA, IFA” refers to the method of testing for ANCA using indirect immunofluorescence assay (IFA). In this test, patient serum is exposed to neutrophils on a slide, and if ANCA antibodies are present, they will bind to the neutrophils. Fluorescently labeled antibodies specific to human IgG are then added, which will bind to any ANCA antibodies attached to the neutrophils. When viewed under a fluorescence microscope, the presence of fluorescence on the neutrophils indicates a positive result for ANCA antibodies.

ANCA testing, particularly via IFA, is an essential tool in the diagnosis and management of ANCA-associated vasculitis. However, it’s important to note that a positive ANCA result does not confirm a diagnosis on its own, as ANCA can also be present in other conditions and in a small percentage of healthy individuals. Diagnosis typically requires a combination of clinical findings, imaging studies, and other laboratory tests, in addition to ANCA testing.

The pattern and staining intensity observed with ANCA testing can provide further information about the subtype of ANCA present, such as cytoplasmic (c-ANCA) or perinuclear (p-ANCA), which may have diagnostic and prognostic significance in certain diseases. Therefore, ANCA testing is an important component of the diagnostic workup for suspected vasculitis and helps guide treatment decisions.