CRP and ankylosing spondylitis: additionally, a significant increase was found in active ankylosing spondylitis, inactive ankylosing spondylitis (group II), and healthy control regarding ESR, CRP, and vitamin D levels, but there were non-significant differences between active ankylosing spondylitis, inactive ankylosing spondylitis and healthy control regarding age, sex, occupation, disease duration, and drug taking (Table 1).