Could IL-1, IL-6, IFN-, and sP-selectin serum levels be considered as objective and quantifiable markers of rheumatoid arthritis severity and activity?

Objectives: Rheumatoid arthritis (RA) is a multisystem, chronic, T-cell-mediated disease in which immunological abnormalities result in symmetrical small joint inflammation, articular destruction due to synovitis, and extra-articular organ involvement. An important role in the pathogenesis of RA is attributed to a combination of genetic factors and environmental triggers. Literature data on the utility of circulating IL-1 beta, IL-6, IFN-gamma, and sP-selectin concentration evaluation depending on the activity and advancement of RA seems to be inconclusive. The aim was a case-control study evaluating IL-1 beta, IL-6, IFN-gamma, and sP-selectin concentrations in 77 RA patients dependent on the Steinbrocker classification as well as the disease activity score with examination of 28 joints (DAS28), and compared to 30 control subjects. Material and methods: Serum IL-1 beta, IL-6, IFN-gamma, and sP-selectin concentrations were measured using ELISA kits. Results: The concentrations of all molecules tested, except for IL-1 beta, were significantly different from the control group. Univariate logistic regression analysis indicated that their levels significantly influenced the likelihood of RA diagnosis. Differences between IL-1 beta, IL-6, IFN-gamma, and sP-selectin concentrations dependent on the disease activity assessed on the basis of the DAS28 score, as well as the severity of the disease assessed based on the Steinbrocker classification, were not observed. IL-6 positively correlated with the DAS28 score. Conclusions: Among the tested molecules, only IL-6 positively correlated with the DAS28 score. Thus, we postulate that next to C-reactive protein and the erythrocyte sedimentation rate, also IL-6 could be clinically relevant and possibly reflects RA activity. Because recently the IL-6 concentration can be determined in applied in vitro diagnostic tests, it presents us with the possibility to test this protein as a marker of RA activity in routine laboratory practice.