Diagnostic significance and antigen specificity of antineutrophil cytoplasmic antibodies in renal diseases. A prospective multicentre study. Italian Group of Renal Immunopathology.

In a prospective multicentre study on the clinical significance of ANCA in renal diseases, sera from 920 patients with rapidly progressive renal failure and/or renal disease in association with extrarenal signs suggestive of a systemic vasculitis were tested for the presence of ANCA by indirect immunofluorescence (IIF) and ELISA. 193 of 920 cases (20.9%) were positive by IIF and 180 (19.5%) by ELISA, using a 'crude' cytoplasmic extract as substrate. The sensitivity and specificity of IIF for 'pauci-immune' cresentic necrotizing GN (CNGN), in association or not with systemic vasculitis, was 87.5 and 95.6% respectively. The IIF pattern and antigen specificity (alpha granules and MPO) correlated well with the clinical features: a cANCA pattern (alpha granules) was associated with ENT involvement (probable Wegener's granulomatosis); a pANCA pattern (MPO) with 'idiopathic' CNGN and small-vessel vasculitis without respiratory tract disease (microscopic polyarteritis); patients with a pulmonary-renal syndrome had either c or pANCA in a similar proportion. Our study confirms a high sensitivity and specificity of ANCA for patients with CNGN. ANCA should be considered an important diagnostic test in patients with renal diseases, especially in the presence of rapidly progressive renal failure.