Addendum to the International Consensus Statement on testing and reporting of antineutrophil cytoplasmic antibodies. Quality control guidelines, comments, and recommendations for testing in other autoimmune diseases.

Antineutrophil cytoplasmic antibody (ANCA) tests are used to diagnose and monitor inflammatory activity in Wegener granulomatosis, microscopic polyangiitis and its renal-limited variant (pauci-immune crescentic glomerulonephritis), and Churg-Strauss syndrome. The International Consensus Statement on testing and reporting of ANCA states that ANCA are demonstrated most readily in these conditions by using a combination of indirect immunofluorescence (IIF) of normal peripheral blood neutrophils and enzyme-linked immunosorbent assays (ELISAs) that detect ANCA specific for proteinase 3 or myeloperoxidase. The group that produced the International Consensus Statement has developed guidelines for the corresponding quality control activities, examples of comments for various IIF patterns and ELISA results, and recommendations for ANCA testing when inflammatory bowel disease and other nonvasculitic ANCA-associated autoimmune diseases are suspected.