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

OBJECTIVE: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). METHODS: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. RESULTS: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. CONCLUSION: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.