ROX variables and ROX index for prediction of invasive mechanical ventilation and its performance according to FiO2
| Se (%) | Sp (%) | PPV (%) | NPV (%) | LR+ | LR− | AUROC | 95% CI | P value | |
| Admission ROX index variables | |||||||||
| SpO2 | 50.5 | 45.0 | 9.6 | 88.6 | 0.91 | 1.09 | 0.57 | 0.49 to 0.65 | 0.052 |
| SaO2 (ABG) | 45.5 | 49.3 | 9.4 | 88.6 | 0.90 | 1.11 | 0.51 | 0.40 to 0.61 | 0.895 |
| RR | 53.8 | 78.1 | 22.0 | 93.6 | 2.45 | 0.59 | 0.63 | 0.55 to 0.70 | <0.001 |
| ROX index | |||||||||
| ROX index from SpO2 | 77.8 | 62.4 | 19.3 | 96.0 | 2.07 | 0.36 | 0.73 | 0.67 to 0.07 | <0.001 |
| ROX index from ABG | 75.1 | 68.4 | 20.4 | 96.2 | 2.38 | 0.36 | 0.78 | 0.70 to 0.85 | <0.001 |
| ROX index according to FiO2 | |||||||||
| ROX index if FiO2 <0.28 | 86.1 | 38.7 | 14.9 | 95.7 | 1.41 | 0.36 | 0.59 | 0.49 to 0.69 | 0.121 |
| ROX index if FiO2 ≥0.28 | 75.3 | 72.1 | 25.1 | 95.9 | 2.70 | 0.34 | 0.79 | 0.72 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.