Indirect immunofluorescence in ANCA testing: past achievements, current indications and future perspectives

Introduction Anti-neutrophil cytoplasmic antibodies (ANCA) are important biomarkers for the diagnosis of ANCA-associated vasculitis. ANCA are, however, also detected in many other inflammatory disorders. ANCA as detected by IIF has revolutionized the diagnostic process of small-vessel vasculitis, whereas its role in other autoimmune disorders has been supportive.Areas covered A comprehensive review of the available literature was conducted using PubMed to identify English-language studies on ANCA testing published up to June 2026. The search included studies evaluating ANCA testing in different forms of vasculitis, connective tissue diseases, inflammatory bowel disease, autoimmune hepatitis, and other relevant diseases. Case series were included, whereas individual case reports were excluded. The literature was prioritized according to its relevance to the scope and objectives of this review.Expert opinion Whereas the development of high-quality immunoassays for PR3-ANCA and MPO-ANCA has replaced the IIF method as a screening test for a diagnosis of AAV, there are several conditions in which the IIF test is still valuable. This is true for patients who are suspected of drug-induced vasculitis, cocaine abuse, and/or endocarditis. Furthermore, in patients with connective tissue disorders, autoimmune liver diseases, inflammatory bowel disease, and some other diseases IIF testing is valuable in certain circumstances as well.