Table 1.

Sensitivity and specificity of the cut points for ferritin:ESR ratio and ferritin alone in cases of sJIA‐MAS vs active sJIA and sJIA‐MAS vs SI

	sJIA‐MAS vs Active sJIA	sJIA‐MAS vs SI
Ferritin:ESR cut point	21.5	11.3
	Sensitivity 82%	Sensitivity 91%
	Specificity 78%	Specificity 93%
Ferritin cut point (ng/ml)	1,045	396.6
	Sensitivity 84%	Sensitivity 92%
	Specificity 66%	Specificity 95%

Abbreviation: ESR, erythrocyte sedimentation rate; MAS, macrophage activation syndrome; SI, systemic infections; sJIA, systemic juvenile idiopathic arthritis.