Urinary type II collagen C-terminal peptide is associated with synovitis and predicts structural bone loss in very early inflammatory arthritis

Objectives In rheumatoid arthritis, high levels of the cartilage turnover biomarker C-terminal cross-linking telopeptide of type II collagen (CTX-II) predict an increased risk of radiological progression. In very early inflammatory arthritis erosions are uncommon, therefore CTX-II requires validation against early markers of inflammatory arthritis such as power Doppler ultrasound (PDUS) synovitis and bone mineral density (BMD) loss. Methods In 50 subjects with 12 weeks or less of inflammatory hand symptoms, urinary CTX-II and PDUS were performed at baseline and hand BMD at baseline and 12 months. CTX-II data were log transformed to a normal distribution. Associations between variables were examined using Pearson's r/Spearman's. correlations. Results The mean 12-month change in BMD was -0.0068 g/cm(2) and the geometric mean for baseline CTX-II/creatinine was 245.89 ng/mmol. Log-transformed baseline CTX-II showed a substantive negative association with change in average BMD over 12 months, controlling for baseline BMD and erythrocyte sedimentation rate (r = -0.359, p = 0.044). The median total PDUS score was 3.0 and baseline CTX-II was significantly associated with baseline total PDUS (Spearman's rho = 0.482, p = 0.002). Conclusion Urinary CTX-II correlates with PDUS synovitis and hand BMD reduction very early in the course of inflammatory arthritis, suggesting that CTX-II has potential as a biomarker in very early inflammatory arthritis.