Correlation between the serum level of IL-17 and rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease. Interleukin-17 (IL-17) has an important role in the pathogenesis of RA. This study aimed to evaluate the correlation between the serum level of IL-17 and the disease activity. In this cross-sectional study, 60 patients fulfilled the American college of rheumatology criteria for RA were recruited. Demographic data of patients including age, gender, and disease duration were recorded and then the serum was taken and analyzed for IL-17 level. The disease activity score (DAS28-ESR) was calculated for all patients and the scores lower than 2.6 were considered as inactive; 2.6 to 3.1 as mild, 3.2 to 5 as moderate and higher than 5 were considered as the severely active. Of 60 patients studied, 23 cases had controlled RA with mean disease duration of 75.37 months and mean IL-17serum level of 144.81±47.83 ng/l and 37 cases had active RA with mean disease duration of 101.78 months and the mean serum level of 237±93.8 ng/l. There was a significant correlation between the serum IL-17 level and disease activity (P<0.001) as well as between the serum level of IL-17 and numbers of inflamed and tender joints, the ESR and visual analogue scale. In patients with active RA, the level of serum IL-17 was significantly higher in severe as compared to mild and moderate activity disease. There is a correlation between the serum level of IL-17 and disease activity score. Therefore, the IL-17 level is an indicator of the disease activity and severity of RA and can be used in follow-up of the disease.