CRP and Sacroiliac arthritis: However, after adjustment for the mSASSS, disease activity parameters (BASDAI and CRP) and gender, the strength of association became very similar for both outcomes: ß = 0.10 (95% CI 0.01 to 0.19) for BASFI and ß = 0.12 (95% CI 0.03 to 0.21) for BASMI, indicating that progression by one radiographic sacroiliitis grade would result in a change of 0.10/0.12 points in the BASMI/BASFI.