Nonsmokers | Smokers | |

Total events n | 360 | 40 |

Positive cases n | 65 | 10 |

Prevalence | 18 | 25 |

Cut-off | +50 | +50 |

Sensitivity | 42 | 68 |

Specificity | 75 | 87 |

PPV | 26 | 63 |

NPV | 86 | 89 |

Accuracy | 69 | 83 |

p-value^{#} | 0.001 | 0.017 |

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 a change from controlled (ACQ score <1.5) to uncontrolled (ACQ score ≥1.5) asthma. A true-positive case was defined as an exhaled nitric oxide fraction (*F*_{eNO}) change of more than or the same as the cut-off value associated with a positive event.*F*_{eNO}exhibited similar operating characteristics in both the nonsmoking and smoking group. In particular, a high NPV was observed.