Autoimmune diseases occur when physiological tolerance to self-antigens is lost and thereafter, human body can not discriminate between self and non-self tissue. In autoimmunity, production of different auto-antibodies result in variety of pathologic manifestations. Auto-antibodies are hallmark of both systematic and organ specific autoimmune diseases. Among various autoantibodies, anti-neutrophil cytoplasmic antibody (ANCA) is a useful diagnostic tool for auto-immune glomerulonephritis. There are many techniques used for the detection of ANCA level. Here, we want to introduce some common...