Diagnostic potential of interleukin-40 (IL-40) in rheumatoid arthritis patients

Abstract

BackgroundRheumatoid arthritis (RA) is the most common type of inflammatory arthritis. Newly emerging evidence has highlighted the role of B-cell produced cytokines in the development and progression of RA. Specifically, the expression of IL-40 has been shown to be significantly increased in affected patients. Patients and methodsThe study included 66 patients attending Rheumatology Unit, Baghdad Teaching Hospital and 66 matched controls. C-reactive protein (CRP), rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) were measured. Disease activity score (DAS28) was assessed. Serum IL-40 levels were assessed using an enzyme-linked immunosorbent assay (ELISA). ResultsThe mean ages of patients were 46.5 ± 10.2 years (23–68 years) and were 55 females and 11 males (F:M 5:1). 4 were smokers. Positivity of CRP, RF and anti-CCP were 75.8 %, 65.2 % and 62.2 % respectively. Steroids were received by 21.2 %, methotrexate by 56.1 %, biologics in the form of etanercept and adalimumab by 86.4 %. IL-40 was significantly higher in patients (9.1 ± 1.3 ng/ml) than in controls (7.5 ± 2.2 ng/ml; p < 0.001). The IL-40 level was comparable between females and males and was not related to smoking, CRP, RF or anti-CCP positivity or to receiving medications. Serum IL-40 showed good validity in diagnosing RA at a cut-off value (≥8.2 ng/ml) and area under curve (AUC) (0.74), the sensitivity was 73.2 %, specificity (66.7 %), and the accuracy (70.5 %)(p < 0.001). ConclusionThe increased level of serum IL-40 and its potential diagnostic role have been revealed in RA. Further studies are needed to be implement and elucidate the complete role of IL-40 in RA.