DIAGNOSTIC-SIGNIFICANCE AND ANTIGEN-SPECIFICITY OF ANTINEUTROPHIL CYTOPLASMIC ANTIBODIES IN RENAL DISEASES - A PROSPECTIVE MULTICENTER STUDY

In a prospective multicentre study on the clinical significance of ANC A in renal diseases, sera from 920 patients with rapidly progressive r enal failure and/or renal disease in association with extrarenal signs suggestive of a systemic vasculitis were tested for the presence of A NCA 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 I IF for 'pauci-immune' crescentic 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) correlat ed well with the clinical features: a cANCA pattern (alpha granules) w as associated with ENT involvement (probable Wegener's granulomatosis) ; a pANCA pattern (MPO) with 'idiopathic' CNGN and small-vessel vascul itis without respiratory tract disease (microscopic polyarteritis); pa tients with a pulmonary-renal syndrome had either, c or pANCA in a sim ilar proportion. Our study confirms a high sensitivity and specificity of ANCA for patients with CNGN. ANCA should be considered an importan t diagnostic test in patients with renal diseases, especially in the p resence of rapidly progressive renal failure.