Analytical and diagnostic accuracy of the EliA™ automated enzyme fluoroimmunoassay for antineutrophil cytoplasmic autoantibody detection

Abstract
Anti-proteinase 3 antineutrophil cytoplasmic antibodies (PR3-ANCA) and anti-myeloperoxidase antibodies (MPO-ANCA) are considered important serological markers for several forms of idiopathic systemic vasculitis. The aim of the study was to verify the analytical and clinical performance of a new automated enzyme fluoroimmunoassay, the EliA system, for PR3-ANCA and MPO-ANCA detection.For this purpose the sera of 52 consecutive well-defined patients with a clinical diagnosis of Wegener’s granulomatosis (WG) (n = 29) or microscopic polyangiitis (MPA) (n = 23), and 70 controls suffering from connective tissue disease (25 systemic lupus erythematosus, 25 Sjögren’s syndrome and 20 rheumatoid arthritis) were tested for PR3-ANCA and MPO-ANCA with the EliA assay (Pharmacia Diagnostics, Freiburg, Germany). For comparison purposes, the same sera were also tested by indirect immunofluorescence, another direct immunometric assay (Varelisa, Pharmacia Diagnostics) and a capture PR3-ANCA (Wieslab AB, Lund, Sweden) method.Both the EliA PR3-ANCA and MPO-ANCA assays showed between- and within-assay precision of < 10%. The dilution test gave straight lines (rThere was a high positive correlation between the EliA and Varelisa methods for quantitative detection of MPO-ANCA levels (rIn conclusion, the EliA MPO-ANCA and PR3-ANCA methods provide good diagnostic accuracy and excellent analytical accuracy, which, in association with the practicality of the automated EliA system, make this method a useful tool for the diagnosis of ANCA-associated vasculitides.

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