BACKGROUND:
Radiographic axial spondyloarthritis (r-axSpA) is associated with extracellular matrix (ECM) remodelling of affected tissues. We investigated whether there was a relationship between biomarkers of ECM remodelling and 2-year radiographic progression in r-axSpA.

METHODS:
Patients from the Outcome in Ankylosing Spondylitis International Study (OASIS) were included if they had serum, clinical and spinal radiographic assessments available at baseline and 2 years later. Two readers independently scored the radiographs according to the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS). The average score was used. Type I, V and VI collagen metabolites (C1M, C5M and C6M) and citrullinated and matrix metalloproteinase-degraded vimentin (VICM) were assessed in serum by ELISAs. The relationship between serum biomarkers and 2-year radiographic progression was investigated using linear regression analyses adjusted for potential confounders. Interactions were tested.

RESULTS:
Patients included (n=122) had a mean age of 45 years (SD 12), 70% were male and 82% were human leucocyte antigen-B27 positive. The mean 2-year mSASSS progression was 2.1 (2.9) units. Only C1M was significantly associated with mSASSS progression (β=0.01, 95% CI 0.00 to 0.03). The effect disappeared after adjustment for confounders. C5M, C6M and VICM showed no relationship with mSASSS progression.

CONCLUSION:
We did not find evidence that degradation of ECM is related to radiographic progression in patients with r-axSpA.