ANCA testing: the current stage and perspectives.

During the past 30 years, remarkable progress has been achieved in understanding the role of the antineutrophil cytoplasmic antibodies (ANCAs) directed against proteinase 3 (PR3) and myeloperoxidase (MPO) in so-called "ANCA-associated vasculitides". In the right clinical context, ANCAs are a good seromarker for these diseases, have improved nomenclature of systemic vasculitides and have contributed to new pathogenic concepts. However, problems with the clinical applications of ANCA testing in daily practice remain. They can be summarised as follows: assay standardisation and performance; the use of ANCA testing in a clinical setting with a low pretest probability; the relationship between ANCA titres and disease activity remains unclear. The solution to problems regarding the ANCA diagnosis is focussed on the fundamental methods, i.e., correct implementation of IFT and ELISA, the cautious use of commercial assays and restricting the use of the tests to clinical situations with a rather high pretest probability of AAV.