Objective: Antineutrophil cytoplasmic antibody (ANCA) is known to be associated with vasculitides. But recently ANCA has been reported in some chronic inflammatory diseases regardless of vasculitic condition. Although the incidence of vasculitis was low in Korea, we occasionally encounter patients with positive ANCA. And it was doubtful whether ANCA positivity of reports, in time that ANCA test was introduced in Korea, was true. So this study aimed to reevaluate the clinical utility of ANCA with the modern stabilized substrate. Methods: 162 patients with positive ANCA from Jan. 2002 to Jan. 2003 were investigated. ANCA was tested by indirect immunofluorescence assay using ALCA kit (ImmunoThink^Ⱂ, Korea). Results: Of 162 patients, 158 were P-ANCA positive, 2 were C-ANCA positive and 2 were atypical C-ANCA positive. Most of the ANCA positive patients had chronic inflammatory diseases-129 patients (79.6%) with rheumatoid arthritis (RA), 4 (2.5%) with lupus and 4 (2.5%) with ulcerative colitis. Only 3 patients (1.9%) had vasculitides and the remaining seventeen patients had other diseases. Among the RA patients with ANCA, 27.9% were seronegative RA. Conclusion: In order to increase the clinical applicability of ANCA test in diagnosing vasculitides, it is essential to decrease the false positivity by using stabilized substrate and by adapting professional interpretation from experts. And our results suggest that ANCA testcan be useful for diagnosing chronic inflammatory diseases such as rheumatic diseases (especially RA) along with vasculitides in Korea. Further study will be needed for the diagnostic utility of ANCA in RA.

Keywords: Antineutrophil cytoplasmic antibody, Rheumatoid arthritis