Recent studies revealed the role of Th17 cells and IL-17A in the pathogenesis of rheumatoid arthritis (RA). However, the clinical usefulness of IL-17 at different stages in the development and progression of RA needs further investigation, including its implication in the diagnostic process or of the patients follow up.
Aims: Our study aimed to assess the systemic and local concentrations of IL-17 in RA, compared to osteoarthritis (OA) patients and healthy controls (HCs) and to establish a possible systemic and local biomarker for RA disease activity and severity.
Methods: A total of fifty-one persons were recruited to the study. Concentrations of IL-17A were assessed in matched serum and synovial fluid(SF) samples from twenty RA patients; and serum samples of fifteen OA patients and sixteen HCs. RA patients were characterized clinically by twenty-three parameters (clinical, laboratory, instrumental).
Results: The local levels of IL-17A in RA patients were higher than the systemic concentrations (8.65±2.98 vs. 0.32±0.06 pg/ml, p=0.012). The ROC curve analysis for synovial IL-17A showed better performance than serum (AUC 0.885 (95% CI: [0.775÷0.995]), р < 0.001, vs. AUC 0.592, respectively). There was no significant difference in the serum IL-17A concentration among studied persons. Serum levels of IL-17A were higher in RA patients with mild activity comparedto those with moderate (p=0.028, p=0.008) and severe activity (p=0.069, p=0.037) determined by the disease activity index (DAS) 28 and the simplified disease activity index (SDAI), respectively. Serum levels of IL-17A correlated negatively with the presence of anemia (p=0.016). Тhe SF levels of IL-17 were higher in patients with elevated ESR, CRP, presence of RF (IgM, IgG, IgA) and anti-CCP antibodies in the serum.
Conclusion: Оur results confirmed the increased levels of IL-17A locally in RA which may play an essential role in the disease activity and progression. Serum concentrations of IL-17A could be used as a possible systemic biomarker for disease activity even in patients with mild disease activity scores or subclinical synovitis.