Anti-neutrophil cytoplasmic antibodies, also known as ANCA, are antibodies that react with neutrophil or monocyte cytoplasmic components of the blood as target antigens, and ANCA is currently detected by indirect immunofluorescence and other immunological methods that target antigen-specific antibodies, such as ELISA. One of the most classical conventional assays. By this method, different fluorescence patterns can be seen under the microscope, and there are usually three types, i.e. cytoplasmic, perinuclear, and atypical. The cytoplasmic type is where the fluorescence is uniformly distributed throughout the cell plasma, with no fluorescence expressed in the nucleus; the perinuclear type is where there is a smooth band of fluorescence around the nucleus of the neutrophil. For the detection of ANCA, the international consensus is to first use indirect immunofluorescence as a screening method, and if positive, then use ELISA to detect specific antigens, and the two methods are best used in combination.