This test is used to detect antibodies in the blood that target proteins in the cytoplasm of neutrophils, a type of white blood cell. The IFA method involves applying the patient’s serum to neutrophils fixed on a slide, then adding a fluorescent-labeled antibody that binds to any ANCA present. Under a fluorescence microscope, a cytoplasmic staining pattern (c-ANCA) indicates the presence of these antibodies.