The following is a summary of  “Relationship Between Inflammation and Radiographic Progression in Patients With Ankylosing Spondylitis Attaining a BASDAI of Less Than 4 During Tumor Necrosis Factor Inhibitor Treatment” published in the December 2022 Issue of Rheumatology by Koo et, al.

Examine the association between inflammation and radiographic advancement in patients with ankylosing spondylitis (AS) receiving tumor necrosis factor inhibitor (TNFi) medication and achieving a Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) of less than4.  From January 2001 to December 2018, medical records data of patients with AS with BASDAI scores less than 4 during TNFi medication were evaluated at 6-month intervals. 

Researchers used linear mixed models with modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) as the response variable, baseline mSASSS, and the cumulative sum of C-reactive protein (CRP) with different lag times (6, 12, 18, 24, 30, and 36 months) as fixed effects, and patients as random effects to examine the association between mSASSS and C-reactive protein (CRP) over time. Additional clinical factors were added to linear mixed models to examine the associations between mSASSS and the total CRP or the lag periods with the highest beta coefficients. In all, 333 patients contributed 2,956 intervals. Significant beta coefficients were found between mSASSS and the sum of log CRP over the preceding 18 to 36 months at various time intervals. 

The final linear mixed model found a statistically significant association between log CRP over the preceding 24 months and mSASSS at 24 months (0.04, 95% CI 0.01-0.07, P=0.004). Even in individuals who achieve a BASDAI of less than 4 while on TNFi therapy, persistent inflammation is still linked to radiographic progression. Although clinical improvement is shown with TNFi therapy, CRP serves as a proxy sign for radiographic advancement.