Sensitivity, specificity, PPV and NPV of different surrogate markers using alternative cut-points to diagnose eosinophilic airway inflammation (less than, more than or equal to 3% sputum eosinophils)
| Threshold | Sensitivity | Specificity | PPV | NPV | |
|---|---|---|---|---|---|
| Blood eosinophils | >0.22×109/L | 86 | 79 | 60 | 93 |
| Blood eosinophils | ≥0.25×109/L | 79 | 84 | 64 | 91 |
| Blood eosinophils | ≥0.27×109/L | 78 | 91 | 79 | 91 |
| FENO level | >20 ppb | 74 | 57 | 40 | 87 |
| FENO level | ≥24 ppb | 74 | 63 | 42 | 87 |
| FENO level | ≥42 ppb | 63 | 92 | 74 | 89 |
| FENO level | >50 ppb | 56 | 92 | 67 | 84 |
| Serum periostin (in-house) | >26 ng/mL | 54 | 57 | 29 | 77 |
NPV, negative predictive value; PPV, positive predictive value.