Demographic characteristic of ankylosing spondylitis in Chinese

Objective: To investigate the demographic characteristic of ankylosing spondylitis (AS) in Chinese. Methods: Three hundred sixty Chinese AS patients in Taiwan were enrolled in this study. These AS patients fulfilled the 1984 modified New York criteria and visited the Outpatient Department of Veterans General Hospital-Taipei. Patients completed the questionnaires, containing disease activity (BASDAI), functional ability (BASFI) and patient's global assessment (BAS-G). Physical examinations were performed to determine the spinal mobility, including modified Schober index (MSI), fingertip-to-floor distance (FFD), lumbar lateral flexion (LLF), and occiput-to-wall distance (OWD) and chest expansion (CE). Results: The mean (S.D) onset age of the 360 AS patients was 23.79 (9.15) y/o and the male-to-female ratio 3.68 (283/77). The HLA B27 positive rate of the AS patients was 91% (328/360). The ratio of the 360 AS patients with history of peripheral joint involvement was 60.3% (217/360), and the ratio of the 360 AS patients with uveitis was 10% (36/360). The mean (S.D) score of the BASDAI, BASFI, and BASG were 4.19 (2.07), 2.69 (2.37), and 5.05 (2.82), respectively. Significant decrease MSI [3.78 (2.21) vs. 4.97 (2.87) cm, p = 0.001] and increased FFD [22.64 (16.36) vs. 16.81 (14.28) cm, p = 0.002] were observed in the male than in the female AS patients. BASDAI [4.72 (2.03) vs. 3.39 (1.87), p < 0.001], BASFI [3.21 (2.51) vs. 1.91 (1.89), p < 0.001], BASG [5.62 (2.81) vs. 4.19 (2.63), p < 0.001] were significantly higher in the AS patients with history of peripheral joint involvement than those without. BASDAI [4.92 (2.21) vs. 4.11 (2.04), p = 0.011] was significantly higher in the AS patients with history of uveitis than those without. BASDAI showed mild correlation with MSI (r = -0.122, p = 0.021), FFD (r = 0.186, p < 0.001) and CE (r = -0.104, p = 0.049). BASFI showed high correlation with FFD (r = 0.485, p < 0.001), and OWD (r = 0.412, p < 0.001), and moderate correlation with MSI (r = -0.365, p < 0.001), CE (r = -0.285, p < 0.001) and LLF (r = 0.249, p < 0.001). Conclusion: The Chinese AS patients in Taiwan predominantly affected young male adult. More severe spinal limitation was found in the male AS patients. Higher disease activity and poor functional ability were observed in the AS patients with history of peripheral joint involvement. The AS patients with uveitis have higher disease activity. Limitation of spinal flexion could be a useful index of functional impairment.