IFNG and macrophage activation syndrome: However, when all sHLH/MAS patients (untreated and treated with glucocorticoids at sampling) were analyzed, we found an AUC of 0.73 (95% CI, 0.58-0.87, p=0.006) for pSTAT1 levels in unstimulated monocytes (Figure 4C) and an AUC of 0.66 (95% CI, 0.50-0.81, p=0.06) for pSTAT1 levels in monocytes stimulated with IFNγ (10 ng/ml) (Figure 4D).