Baseline serum biomarkers of inflammation, bone turnover and adipokines predict spinal radiographic progression in ankylosing spondylitis patients on TNF inhibitor therapy

To analyze whether biomarker levels at baseline or their change after 3 months or 2 years predict radiographic spinal progression in ankylosing spondylitis (AS) patients treated with TNF-α inhibitors (TNFi). 137 AS patients from the Groningen Leeuwarden Axial Spondyloarthritis (GLAS) cohort were included before starting TNFi. Serum biomarkers were measured at baseline, 3 months and 2 years: Markers of inflammation (calprotectin, matrix metalloproteinase-3, vascular endothelial growth factor), bone turnover markers (bone-specific alkaline phosphatase, serum C-terminal telopeptide fragments of type I collagen (sCTX), osteocalcin, osteoprotegerin, procollagen type I and II N-terminal propeptide, sclerostin) and adipokines (high-molecular-weight adiponectin, leptin, visfatin). Spinal radiographs were scored at baseline, 2 and 4 years. Logistic regression was performed to examine the association between biomarker values and radiographic spinal progression, adjusting for known risk factors for radiographic progression. Baseline calprotectin and visfatin levels were associated with mSASSS progression ≥2 points (OR 1.195 [95%CI 1.055–1.355] and 1.465 [1.137–1.889], respectively), while calprotectin was also associated with new syndesmophyte formation after 2 years (OR 1.107 [1.001–1.225]). Baseline leptin level was associated with mSASSS progression ≥4 points after 4 years (OR 0.614 [0.453–0.832]), and baseline sCTX level with syndesmophyte formation after 4 years (OR 1.004 [1.001–1.008]). Furthermore, change of visfatin and leptin levels over the first 2 years showed significant association with radiographic progression after 4 years. Independent of known risk factors, serum levels of biomarkers at baseline are able to predict radiographic spinal progression over 2 and 4 years in AS patients on TNFi therapy.