Besides, there have been advances in assay setup (antigen presentation) with development of second (capture-based) and third (anchor-based) generation assays. Over the last 15 years, the performance of ELISA has improved and novel, sensitive and automated technologies, such as fluoro-enzyme immunoassay, chemiluminescence assay and multiplexed flow immunoassay, have been introduced. 4 Although this consensus is still widely applied, the position of IIF is being questioned. Serum samples containing ANCA should be tested in ELISAs for PR3-ANCA and MPO-ANCA”. For ANCA testing in "new" patients, IIF must be performed on all serum samples. Paradigm shift in ANCA diagnostic: New international consensus recommendationsĪn international consensus statement for ANCA testing was issued in 1999 and states that “ ANCA is best demonstrated by using a combination of indirect immunofluorescence (IIF) and enzyme-linked immunosorbent assays (ELISAs) that detect ANCA specific for proteinase 3 (PR3) or myeloperoxidase (MPO). This review considers current data on ANCA testing, presents the new international consensus on ANCA testing, and discusses the usefulness of PR3- and MPO-ANCA in the diagnosing and managing of patients with small-vessel vasculitis. In the right clinical context, a positive test for PR3- or MPO-ANCA has high sensitivity and specificity for a diagnosis of AAV. 6,7 Furthermore, there is a need for screening algorithm including clinical gating policies to guide the flow of analysis in diagnostic laboratories.
4,5 Since the establishment of this consensus, many new antigen specific immunoassays have become available, and this has challenged the position of IFT in the testing algorithm for ANCA in vasculitis. Ideally all three tests should be used in each sample. 2,3ĭetection of ANCA in vasculitis is based on primary screening by immunofluorescence test (IFT) on ethanol-fixed neutrophils, and positive indirect immunofluorescence (IIF) test should always be followed by specific PR3- and MPO-ANCA immunoassays ( Figure 1). However, ANCA has limited specificity as it can be demonstrated in patients with inflammatory bowel disease (IBD), autoimmune liver disease, connective tissue diseases, infections and drug-induced vasculitis, often with multiple antigen specificities and unclear clinical significance. 2 Two ANCA are highly associated markers for ANCA-associated vasculitis (AAV), the latter of which includes granulomatosis with polyangiitis (GPA ), microscopic polyangiitis (MPA), eosinophil granulomatosis with polyangiitis (EGPA), and primary pauci-immune crescentic glomerulonephritis, namely C-ANCA synonymous with cytoplasmic fluorescence and specificity for proteinase 3 (PR3-ANCA), and P-ANCA with perinuclear fluorescence and specificity for myeloperoxidase. 1 The spectrum of diseases associated with ANCA has since increased. The detection of anti-neutrophil cytoplasmic antibody (ANCA) as a diagnostic tool and marker of disease in Wegener’s granulomatosis was described in 1985 by Van der Woude and coworkers.
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