Serum YKL-40 concentrations in patients with early rheumatoid arthritis: relation to joint destruction.

OBJECTIVE YKL-40 is a secretory glycoprotein of chondrocytes, synovial cells, macrophages, and neutrophils. The aims were to determine serum YKL-40 in patients with early rheumatoid arthritis (RA) and seek associations with early joint erosions. METHODS YKL-40 was measured by ELISA in serum samples collected every three month for 36 months from patients with early RA. The patients were treated with DMARDs and some were allocated to additional prednisolone. RESULTS Serum YKL-40 was higher in RA patients compared with controls (98 vs. 42 microg/l, p<0.001). The mean serum YKL-40 during the study correlated with the progression in Larsen score (Pearson's test: p=0.004). Patients with a persistently high serum YKL-40 had larger progression in Larsen score compared with patients with normal serum YKL-40 (median progression: 7 vs. 0, p=0.003). CONCLUSION These data suggest that elevated serum YKL-40 is related to progression in joint destruction in early RA patients.