In contrast, S100A4 levels did not correlate with disease activity as determined by BASDAI or CRP levels (r = − 0.197, p = 0.139; r = − 0.219, p = 0.099; respectively) and did not differ between patients with or without peripheral joint involvement or other clinical manifestations such as psoriasis, inflammatory bowel disease or presence of uveitis (Additional file 1). Here, CRP is linked to uveitis.