Comparisons of the diagnostic values between R5 and spirometric parameters
| AUC (95% CI) | p-value | Cut-off | Sensitivity | Specificity | |
| Respiratory diseases | |||||
| R5 z-score | 0.807 (0.790–0.824) | <0.01 | >1.426 | 62.4% | 90.3% |
| FEV1 z-score | 0.900 (0.888–0.912) | <0.01 | ≤ −1.112 | 74.0% | 95.4% |
| FEV1/FVC z-score | 0.861 (0.847–0.875) | <0.01 | ≤ −1.410 | 70.5% | 97.4% |
| Obstructive airway diseases | |||||
| R5 z-score | 0.788 (0.770–0.806) | <0.01 | >1.426 | 66.7% | 81.5% |
| FEV1 z-score | 0.820 (0.803–0.837) | <0.01 | ≤ −1.069 | 76.2% | 75.2% |
| FEV1/FVC z-score | 0.922 (0.912–0.933) | <0.01 | ≤ −1.401 | 80.72% | 94.5% |
| UAO | |||||
| R20 z-score | 0.895 (0.852–0.938) | <0.01 | >2.300 | 87.5% | 79.0% |
| FEV1 z-score | 0.509 (0.420–0.598) | 0.84 | ≤ −0.230 | 82.1% | 26.6% |
| 0.557 (0.473–0.640) | 0.18 | ≤ −0.595 | 87.2% | 32.2% | |
| PEF z-score | 0.728 (0.657–0.799) | <0.01 | ≤−0.835 | 89.47% | 47.87% |
AUC: area under the curve; respiratory diseases: interstitial lung disease+asthma+COPD+bronchiectasis+upper airway obstruction (UAO) versus healthy; R5: resistance at 5 Hz; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; obstructive airway diseases: asthma+COPD+bronchiectasis+UAO versus healthy+ILD; R20: resistance at 20 Hz; PEF: peak expiratory flow.