Interleukin-17 as a predictor of subclinical synovitis in the remission state of rheumatoid arthritis.

Objectives: To compare the level of pro and anti-inflammatory cytokines, and angiogenic mediators between Rheumatoid arthritis (RA) patients with and without subclinical synovitis (SS) in remission state, to find the correlation of these mediators with Greyscale synovitis (GSS) and power Doppler (PD) scores, and to find the probable predictor/s of SS.

Methods: 52 RA patients in remission state were recruited and subdivided into with and without SS group by Ultrasonography (USG) of 14 joints. Total GSS and PD scoring was done. The serum levels of the pro/anti-inflammatory cytokines and angiogenic mediators were compared between groups, and correlation and regression analysis were done with GSS and PD scores.

Result: 63.46% patients had USG evidence of SS. Patients with SS had significantly higher levels of pro-inflammatory and angiogenic mediators [matrix-metalloproteinase -3 (p = 0.0001), Tumour necrosis factor-α (p = 0.0001), Interleukin (IL)-6 (p = 0.001), IL-1b (p = 0.0001), IL-17 (p = 0.0005), IL-33 (p = 0.0003), Tie-2 (p = 0.0001), vascular endothelial growth factor (VEGF (p = 0.03)], and lower anti-inflammatory cytokines [IL-27 (p = 0.0003), IL-10(p = 0.0001)]. A strong positive correlation of GSS score was noted with IL-17(r = 0.7), IL-6 (r = 0.7), IL-1b (r = 0.7), and IL-33 (r = 0.6). Multiple linear regression model identified IL-17 and IL-6 as predictors of GSS score, and TNF-α and VEGF as predictors of PD score. IL-17 level > 249 picogram/millilitre (pg/ml) could predict the SS with high specificity (89.5%).

Conclusion: Patients with SS in the remission state of RA showed altered expression of some of the pro/anti-inflammatory/angiogenic markers compared to those not having SS. IL-17, IL-6, VEGF, and TNF-α could be the predictors of USG synovial scores.