[Neutrophil anticytoplasmic antibodies: their diagnostic utility in vasculitis and glomerulonephritis]

The prevalence and diagnostic usefulness of antineutrophil cytoplasmic antibodies (ANCA) were analyzed in a series of patients with different types of vasculitis, connective tissue diseases, nephropathies and lung diseases.

Six hundred seventy-six consecutive patients with systemic vasculitis, connective tissue diseases, nephropathies and different lung disturbances were included in the study. The ANCA were determined by indirect immunofluorescence (IIF) on neutrophils fixed in ethanol. For the detection of antimyeloperoxidase (MPO) antibodies (Ab) a new technique was developed consisting in the performance of IIF on neutrophils with a deficiency in MPO. The serologic samples were also analyzed by enzyme-linked immunosorbent assays with MPO and purified proteinase 3 (PR3).

ANCA were demonstrated in 95 patients. A cytoplasmic pattern (c-ANCA) was detected in 25 cases (26%) and in 70 (74%) a perinuclear pattern (p-ANCA) was observed. Twenty-one of the 25 cases (84%) of c-ANCA corresponded to anti-PR3 Ab and 61 of the 70 (87%) of p-ANCA corresponded to anti-MPO Ab. The anti-PR3 Ab identified Wegener's granulomatosis, with a sensitivity and specificity for the generalized and clinically active forms being 65 and 88%, respectively. The anti-MPO Ab were principally detected in patients with rapidly progressive glomerulonephritis (RPGN) and hemorrhagic alveolar capillaritis. The sensitivity and specificity of the anti-MPO Ab for the RPGN and alveolar capillaritis were 75% and 98%.

Two principal subtypes of ANCA may be detected, which also recognize two fundamental clinicopathologic entities. The high diagnostic sensitivity and specificity of these antibodies for each of the processes to which they are associated can justify the adoption of therapeutic measures in determined cases.