In the linear regression analysis of the association between BASFI/BASMI change scores over 2 years with the absolute change in the sacroiliitis sum score, ß was 0.03 (95% CI -0.19 to 0.25) and 0.25 (95% CI 0.03 to 0.47), respectively, adjusted for the mSASSS change score, BASDAI change score, time-averaged CRP over two years, and sex. This evidence concerns the gene CRP and Sacroiliac arthritis.