Table 3

ROX variables and ROX index for prediction of invasive mechanical ventilation and its performance according to FiO2

Se (%)Sp (%)PPV (%)NPV (%)LR+LR−AUROC95% CIP value
Admission ROX index variables
 SpO250.545.09.688.60.911.090.570.49 to 0.650.052
 SaO2 (ABG)45.549.39.488.60.901.110.510.40 to 0.610.895
 RR53.878. to 0.70<0.001
ROX index
 ROX index from SpO277.862.419.396.02.070.360.730.67 to 0.07<0.001
 ROX index from ABG75.168.420.496.22.380.360.780.70 to 0.85<0.001
ROX index according to FiO2
 ROX index if FiO2 <0.2886.138.714.995.71.410.360.590.49 to 0.690.121
 ROX index if FiO2 ≥0.2875.372. to 0.85<0.001
  • ABG, arterial blood gases; AUROC, area under the curve of receiver operating characteristics; FiO2, fraction of inspired oxygen; LR+, likelihood ratio of a positive test; LR−, likelihood ratio of a negative test; NPV, negative predictive value; PPV, positive predictive value; ROX index, Respiratory rate-OXygenation index; RR, respiratory rate; SaO2, arterial oxygen saturation; Se, sensitivity; Sp, specificity; SpO2, oxygen saturation by pulse oximetry.