Antineutrophil Cytoplasmic Antibodies Testing and Interpretation.

The discovery of antineutrophil cytoplasmic antibodies (ANCA) helped establish ANCA-associated vasculitis as a separate and well-defined clinical entity. Its progressive incorporation into the clinical diagnosis algorithms has made ANCA testing a cornerstone immunoassay embedded in the management of ANCA-associated vasculitis. After its description by indirect immunofluorescence, proteinase-3 and myeloperoxidase were identified as principal ANCA targets. ANCA, and proteinase-3 and myeloperoxidase immunoassessment, have undergone iterative rounds of improvement in sensitivity and specificity. This article traces landmarks in the development of ANCA tests, describes common pitfalls arising during ANCA interpretation, and discusses new technologies to improve the future of ANCA testing.