Anti-neutrophilic cytoplasmic antibody (ANCA) has been reported in systemic sclerosis (SSc). Some clinical features of SSc can also be presented with ANCA-associated vasculitis. Objectives were to determine the prevalence and clinical associations with ANCA among Thais with SSc.

Material and methods:
A cross-sectional study of Thai adult SSc patients was conducted. According to the sample size calculation, 185 patients were included. Clinical and laboratory tests for serology and others for evaluation of the clinical association with ANCA were done simultaneously on the study date.

The female to male ratio was 2 : 1. The majority had the diffuse SSc subset (71.2%). The respective prevalence of having a) at least 1 serological test for ANCA (viz., perinuclear ANCA, cytoplasmic ANCA, anti-myeloperoxidase, or anti-proteinase3), b) positive for either p-ANCA or c-ANCA, c) positive for either anti-MPO or anti-PR3, d) p-ANCA and anti-MPO and e) c-ANCA and anti-PR3 was 21.6% (95% CI: 15.9–28.3), 11.9% (95% CI: 7.6–17.4) and 13.0% (95% CI: 8.5–18.7) and 1% (95% CI: 0.1–3.9). By multivariate analysis, the erythrocyte sedimentation rate elevation was significantly associated with the presence of the antibody (OR = 11.36, 95% CI: 1.44–83.65), while elevation of high sensitivity cardiac troponin-T (hs-cTnT) was significantly associated with the presence of either p-ANCA or c-ANCA (OR = 4.25, 95% CI: 1.41–15.34). None of the patients had clinical features of systemic vasculitis.

Around one-fifth of SSc patients have detectible ANCA without any features of vasculitis. The presence of ANCA is associated with inflammation and myocardial injury. ANCA is not antibody specific for vasculitis in SSc.