Serum YKL-40 levels and disease characteristics in patients with rheumatoid arthritis

The present study aimed to evaluate serum YKL-40 levels in patients with rheumatoid arthritis (RA) compared to healthy subjects and to search whether there is an association between YKL-40 levels and disease characteristics in RA. In this cross-sectional study, 60 RA patients based on the ACR/EULAR 2010 criteria and 30 age- and sex-matched healthy controls were included. In patients, clinical examination was performed and disease activity score 28 (DAS-28) measure of disease activity was assessed. Serum YKL-40 level was measured using ELISA kit. The mean±SD age of patients and controls was 54.86±11.65 and 50.71±3.72 years, respectively). Serum YKL-40 level was significantly higher in RA patients (951.63±639.98 pg/mL) compared to healthy controls (444.92±150.37 pg/mL) (P<0.001). There was no significant difference in serum YKL-40 level according to the activity of disease (p>0.05). There were significant positive correlations between serum YKL-40 level with disease activity (r=0.347, P=0.007) and rheumatoid factor (r=0.396, P=0.002). There were no significant correlations between serum YKL-40 level with demographic characteristics as well as biochemical measurements including serum creatinine, blood urea nitrogen, erythrocyte sedimentation rate, C-reactive protein and anti-cyclic citrullinated peptide. Our study revealed higher serum YKL-40 levels in RA patients compared to healthy controls, which correlated positively with disease activity. Therefore, YKL-40 can be considered as a novel biomarker for disease activity estimation in RA.