CRP and anemia: The results showed that female gender (OR = 7.695, 95% CI: 3.033 ~ 19.518), being underweight (OR = 0.33, 95% CI: 0.164 ~ 0.662), ossification (OR = 3.013, 95% CI: 1.307 ~ 6.945), abnormal CRP (OR = 2.565, 95% CI: 1.086 ~ 6.061), and abnormal ESR (OR = 4.376, 95% CI: 1.854 ~ 10.332) were independent risk factors for anemia in ankylosing spondylitis patients, with statistically significant differences (P <  0.05) (Table 3).