To investigate whether short-term changes in serum biomarkers of type II collagen degradation (C2C) and types I and II collagen degradation (C1,2C), as well as the biomarker for the synthesis of type II procollagen (CPII) can predict radiographic progression at 1 year following initiation of biologic therapy in patients with inflammatory arthritis.
Serum levels of biomarkers were measured at baseline and at 1, 3, 6, 9, and 12 months after initiation of biologic therapy. A composite score reflecting changes from baseline in all 3 biomarkers (DeltaCOL) was calculated. Associations with clinical responses according to the 28-joint count Disease Activity Score and with radiographic progression according to the modified Sharp/van der Heijde score (SHS) were assessed.
The 1-year increase in the SHS correlated with the 1-month change in C2C results (r = 0.311, P = 0.028) and the DeltaCOL score (r = 0.342, P = 0.015). Radiographic progression was predicted by increases in serum C2C at 1 month (P = 0.031). The DeltaCOL score was significantly associated with 1-year radiographic progression after 1 (P = 0.022), 3 (P = 0.015), 6 (P = 0.048), and 9 (P = 0.019) months of therapy. Clinical remission was predicted by 1-month decreases in serum levels of C2C (P = 0.008) and C1,2C (P = 0.036). By regression analysis, 1-month changes in C2C, C1,2C, and CPII levels were independently associated with, and correctly predicted radiographic outcome in, 88% of the patients.
Short-term changes in serum levels of collagen biomarkers following initiation of biologic therapy may better predict long-term clinical and radiographic outcomes. These collagen biomarkers may therefore be valuable new early indicators of short-term biologic treatment efficacy in clinical trials and in individual patients with inflammatory erosive arthritis.