Cross-sectional assessment of asthma control
| Nonsmokers | Smokers | |
| Total events n | 411 | 59 |
| Positive cases n | 197 | 15 |
| Prevalence | 48 | 25 |
| Cut-off ppb | 50 | 25 |
| Sensitivity | 72 | 66 |
| Specificity | 56 | 48 |
| PPV | 61 | 30 |
| NPV | 68 | 81 |
| Accuracy | 64 | 53 |
| p-value# | <0.001 | 0.39 |
Data are presented as %, unless otherwise indicated. PPV: positive predictive value; NPV: negative predictive value. #: the p-value was defined as the statistical significance of rejecting an area under the curve of 0.5. A positive event was defined as controlled asthma (Asthma Control Questionnaire score <1.5). A true-positive case was defined as an exhaled nitric oxide fraction (FeNO) of less than or the same as the cut-off value associated with a controlled asthma. FeNO does not discriminate for or against cross-sectionally controlled versus uncontrolled asthma in smoking patients (p = 0.39).