In a secondary care setting, ELISA performs best as first test to rule out and rule in AAV, and a second test should be considered not only per consensus guidelines but also when there is clinical doubt and a positive first test, to increase specificity and PPV and reduce false positives.
The majority of ANCA-positive patients in this secondary care setting did not have AAV.
Both IIF and ELISA as first-line tests showed good negative predictive values for ruling out AAV.
ELISA as first-line test showed higher positive predictive value and specificity compared to IIF as first-line test.
ANCA concentrations were higher in AAV patients than in non-AAV patients, but the ranges were wide and overlapping.
The authors propose adding a second confirmatory test when there is clinical doubt and a positive first test, beyond the existing 2017 consensus recommendations.
The 2017 ANCA testing consensus was based on data from tertiary referral centres with relatively high AAV prevalence, which may limit its applicability to secondary care settings.
The study retrospectively collected clinical data on 5518 patients screened for ANCA between 2012 and 2023 at a single centre.
This research looked at how well blood tests for a group of diseases called ANCA-associated vasculitis (AAV) — serious conditions where the immune system attacks small blood vessels — perform in a general teaching hospital setting compared to highly specialized referral centers. Researchers reviewed over 5,500 patients tested for ANCA antibodies over an 11-year period and found that only about 5% tested positive, and of those, nearly two-thirds did NOT have AAV. Instead, many ANCA-positive patients had other autoimmune diseases, cancers, infections, or were taking certain medications that can trigger a positive result. The study compared two types of tests: indirect immunofluorescence (IIF), a microscopy-based method, and ELISA, a more targeted chemical detection method. Both were good at ruling out AAV when negative. However, ELISA was better at correctly identifying true AAV cases (higher specificity and positive predictive value), meaning fewer false alarms. Adding a second confirmatory test when the first was positive made results even more reliable. The existing international guidelines from 2017 already recommend a second test in some situations, but the authors suggest also doing a second test when there is clinical uncertainty and the first test is positive — a refinement that could reduce unnecessary worry and investigation in patients who do not actually have AAV. This research suggests that testing guidelines developed for specialized vasculitis centers may need to be adapted for general hospital settings, where AAV is less common among patients being tested and the risk of false-positive results is therefore higher. Using ELISA as the first test and adding confirmatory testing when results are borderline or uncertain could help doctors more accurately diagnose — or rule out — this rare but serious disease in everyday clinical practice.
Wester Trejo M, Kuijper T, Waverijn G, Bajema I, van den Dorpel R, Kok M, et al.. (2026). ANCA testing strategies: A single centre experience over the past decade in a large teaching hospital in the Netherlands.. PloS one. https://doi.org/10.1371/journal.pone.0357495