Tissue metabolite of type I collagen, C1M, and CRP predicts structural progression of rheumatoid arthritis

Abstract Background Biomarkers of rheumatoid arthritis (RA) disease activity typically measure inflammation or autoimmunity (e.g. CRP, RF). C1M and C3M, metabolites of type I and III collagen, are markers reflecting tissue metabolism. These markers have been documented to provide additional prognostic and predictive value compared to commonly used biomarkers. We investigated the relationship of high serum levels of C1M or C3M to radiographic progression, and benchmarked them to CRP and RF. Methods Placebo treated patients of the OSK1, 2 and 3 studies (Phase III clinical trials testing efficacy of fostamatinib) with baseline serum biomarkers C1M, C3M, CRP and RF were included (nBL = 474). Van der Heijde mTSS was calculated at baseline and 24-week (n24 = 261). Progression was defined as moderate or rapid by ΔmTSS ≥0.5 or ≥ 5 units/year. Patients were divided into subgroups; low (L), high (H) or very high (V) C1M, C3M and CRP, or RF negative, positive and high positive. Difference in clinical parameters were analyzed by Mann-Whitney or χ2tests, and modelling for prediction of progression by logistic regression including covariates (age, gender, BMI, and clinical assessment scores). Results Levels of C1M, C3M, CRP and RF were significantly (p