Immunofluorescence (IF) on ethanol-fixed neutrophils is used to detect ANCA, although formalin-fixed neutrophils may be used to help differentiate ANCA patterns. ANCA can be divided into four patterns when visualised by IF; cytoplasmic ANCA (c-ANCA), C-ANCA (atypical), perinuclear ANCA (p-ANCA) and atypical ANCA (a-ANCA), also known as x-ANCA. c-ANCA shows cytoplasmic granular fluorescence with central interlobular accentuation. C-ANCA (atypical) shows cytoplasmic staining that is usually uniform and has no interlobular accentuation. p-ANCA has three subtypes, classical p-ANCA, p-ANCA without nuclear extension and granulocyte specific-antinuclear antibody (GS-ANA). Classical p-ANCA shows perinuclear staining with nuclear extension, p-ANCA without nuclear extension has perinuclear staining without nuclear extension and GS-ANA shows nuclear staining on granulocytes only. a-ANCA often shows combinations of both cytoplasmic and perinuclear staining.