USE OF ANTINEUTROPHIL CYTOPLASMIC AUTOANTIBODIES IN DIAGNOSING VASCULITIS IN A CHINESE PATIENT POPULATION

Antineutrophil cytoplasmic autoantibodies (ANCA) have been used as mar kers of systemic vasculitides, including microscopic polyarteritis (MP A) and Wegener's granulomatosis. The diagnostic potential of ANCA assa ys together with antibodies against the neutrophil enzymes myeloperoxi dase (MPO) and proteinase 3 for detecting a systemic vasculitis was te sted in a Chinese patient population. 672 sera were received for ANCA assay, and ANCA detected by indirect immunofluorescence was positive i n 73 sera from 42 patients. Of the 42 patients, 3 had cytoplasmic ANCA , while 39 had a perinuclear pattern. There was no patient with Wegene r's granulomatosis. Two cytoplasmic ANCA positive patients suffered fr om ulcerative colitis. Another cytoplasmic ANCA positive patient was a carrier of human immunodeficiency virus. Of the 39 perinuclear ANCA p ositive patients, 10 had MPA. Eight of them were tested for anti-MPO a ntibody, and all were positive. Other immune disorders that were perin uclear ANCA positive included: 13 patients with systemic lupus erythem atosus, 3 with mixed connective tissue disease, 1 with Goodpasture's s yndrome, 2 with inflammatory bowel disease, and 2 patients with IgA ne phropathy. Anti-MPO antibody was not specific for MPA, and 7 out of th e 13 patients with systemic lupus erythematosus were anti-MPO antibody positive. Our study suggests that ANCA and anti-MPO antibody are not specific for MPA in a Chinese population. They would alert the clinici an of the possibility of vasculitis, but a clinicopathological correla tion is essential in making the diagnosis.