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

Objective: YKL-40 is a secretory glycoprotein of chondrocytes, synovial cel ls, macrophages, and neutrophils. The aims were to determine serum YKL-40 i n 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 thre e month for 36 months from patients with early RA. The patients were treate d with DMARDs and some were allocated to additional prednisolone. Results: Serum YKL-40 was higher in RA patients compared with controls (98 vs. 42 mug/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 sco re compared with patients with normal serum YKL-40 (median progression: 7 v s. 0, p = 0.003). Conclusion: These data suggest that elevated serum YKL-40 is related to pro gression in joint destruction in early RA patients.