Original Article

Rheumatology International

, Volume 33, Issue 2, pp 341-346

First online:

Relationship between sonographic parameters and YKL-40 levels in rheumatoid arthritis

  • Maria KazakovaAffiliated withDepartment of Medical Biology, Medical University-Plovdiv
  • , Anastas BatalovAffiliated withDepartment of Rheumatology, Medical University-Plovdiv
  • , Tanya DenevaAffiliated withDepartment of Clinical Laboratory, Medical University-Plovdiv
  • , Nonka MatevaAffiliated withDepartment of Health Management, Health Economics and General Medicine, Medical University-Plovdiv
  • , Zlatimir KolarovAffiliated withClinic of Rheumatology, Medical University-Sofia
  • , Victoria SarafianAffiliated withDepartment of Medical Biology, Medical University-Plovdiv Email author 

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YKL-40, also known as human cartilage glycoprotein 39, is a member of the “mammalian chitinase-like proteins” family without chitinase activity. Increased serum concentrations are associated with inflammatory processes and several types of cancer. In this study, we evaluated YKL-40 levels in serum and synovial fluid of patients with rheumatoid arthritis in comparison with the ultrasonographic findings. YKL-40 levels were measured by enzyme-linked immunosorbent assay in 25 patients with active rheumatoid arthritis and in 40 healthy subjects. B mode and power Doppler were performed to determine synovial thickening and vascularization. Serum YKL-40 level in patients was significantly higher than the concentration in healthy controls (P < 0.01). In patients with rheumatoid arthritis, the level of the glycoprotein in synovial fluid was remarkably elevated compared to the serum level (P = 0.003). The B mode and power Doppler scores correlated to YKL-40 in serum and synovial fluid (P = 0.07). Serum YKL-40 levels were related positively to serum markers of inflammation such as C-reactive protein (P = 0.004) and erythrocyte sedimentation rate (P = 0.003). This study is the first to demonstrate a relationship between YKL-40 levels and ultrasonographic examinations in Bulgarian patients with rheumatoid arthritis. The findings suggest that YKL-40 might be implicated in the pathogenesis of the disease and could indicate the level of joint inflammation.


Joint sonography YKL-40 Rheumatoid arthritis