Correlations between active IL-18 and other cytokines, clinical parameters, and the reactive hemophagocytic syndrome diagnostic score (HScore) were evaluated, and discriminative performance was assessed using receiver operating characteristic analysis.<h4>Results</h4>Serum levels of active IL-18 were significantly higher in patients with AOSD than in those with RA, FMF, and HCs (all p < 0.001). Here, IL18 is linked to rheumatoid arthritis.