PROSPECTIVE-STUDY OF ANTINEUTROPHIL CYTOPLASMIC AUTOANTIBODY TESTS INTHE DIAGNOSIS OF IDIOPATHIC NECROTIZING-CRESCENTIC GLOMERULONEPHRITISAND RENAL VASCULITIS

We prospectively assessed the value of anti-neutrophil cytoplasmic aut oantibodies (ANCA) and nuclear or perinuclear anti-neutrophil autoanti bodies measured by indirect immunofluorescence microscopy and antimyel operoxidase autoantibodies measured by a solid-phase assay in the diag nosis of idiopathic (pauci-immune) necrotizing-crescentic glomerulonep hritis (NCGN) and renal vasculitis at our institution. A diagnosis was established on the basis of clinical and renal biopsy findings, and f ollow-up continued for at least 6 months. ANCA were measured at the co nclusion of the study. Of the 111 study patients, 28 had NCGN and rena l vasculitis. The immunofluorescence assay had 50% sensitivity and 79% specificity. The combination of the enzyme-linked immunosorbent assay for antimyeloperoxidase autoantibodies and the immunofluorescence ass ay for cytoplasmic ANCA had 78% sensitivity and 84% specificity. A fir m diagnosis was established before the determination of ANCA in 26 of the 28 patients with NCGN and renal vasculitis. The antimyeloperoxidas e autoantibody values would have suggested the diagnosis in the other two patients. Of these 28 patients, 5 had negative ANCA results. High antimyeloperoxidase autoantibody values were detected in patients with NCGN and renal vasculitis, whereas lower values were less specific an d were detected mainly in patients with anti-glomerular basement membr ane antibody disease and lupus glomerulonephritis.