Table 4. Demographic characteristics of the AS patients and controls.

Characteristics	Cases(n = 468)	Controls(n = 480)	P value
Sex (male/female)	320/148	327/153	0.944
Age, years, mean ± SD	32.75 ± 11.18	37.84 ± 14.31	0.692
HLA-B27 (+)	460/468	0/480	< 0.001
CRP (mg/L)	10.1 (2.9–25.3)*	----
C3 (g/L)	1.108 ± 0.280	----
C4 (g/L)	0.255 ± 0.092	----

Data was analysed by Chi-square tests.

Data are presented as mean ± standard deviation and median (interquartile range)^*.