Table 3. Metrics of optimal cut point analysis of PaO2/FiO2 ratio, ROX index, and modified ROX index.

AUC, area under the curve; PaO₂/FiO₂, partial pressure of oxygen in arterial blood to the fraction of inspired oxygen ratio; ROX, respiratory rate and oxygenation index

Score	AUC	Optimal cut point	Accuracy	Sensitivity	Specificity
PaO2/FiO2 ratio	0.851	123.6	0.84	0.87	0.81
ROX index	0.848	5.63	0.79	0.68	0.95
Modified ROX index	0.872	4.94	0.85	0.81	0.90