Assessment of asthma control improvement(change in Asthma Control Questionnaire (ΔACQ) <-0.5)
| Nonsmokers# | Smokers# | |||||||||
| Total | D ≤500¶ | D >500¶ | ACQ <2+ | ΔD 0§ | Total | D ≤500¶ | D >500¶ | ACQ <2+ | ΔD 0§ | |
| Total events n | 643 | 306 | 337 | 432 | 301 | 92 | 35 | 57 | 53 | 47 |
| Positive cases n | 257 | 116 | 141 | 112 | 108 | 40 | 14 | 26 | 18 | 15 |
| Prevalence | 40 | 38 | 42 | 26 | 36 | 43 | 41 | 46 | 34 | 32 |
| Sensitivity | 64 | 74 | 55 | 60 | 53 | 57 | 62 | 50 | 56 | 67 |
| Specificity | 71 | 67 | 74 | 70 | 66 | 74 | 84 | 71 | 77 | 75 |
| PPV | 61 | 58 | 60 | 41 | 47 | 62 | 75 | 59 | 56 | 57 |
| NPV | 74 | 80 | 70 | 83 | 72 | 70 | 78 | 63 | 77 | 83 |
| Accuracy | 68 | 70 | 66 | 66 | 65 | 66 | 77 | 61 | 70 | 72 |
| p-valueƒ | <0.001 | <0.001 | <0.001 | <0.001 | 0.002 | <0.001 | <0.001 | 0.070 | <0.001 | <0.001 |
Data are presented as %, unless otherwise indicated. PPV: positive predictive value; NPV: negative predictive value. #: cut-off value of -20%; ¶: inhaled corticosteroid (ICS) dose (D) in μg equivalents of beclomethasone diproprionate·day−1; +: ACQ <2 tested the subgroup with an initial ACQ score of <2; §: ΔD 0 tested the subgroup without treatment modification between consecutive visits; ƒ: 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 an improvement in asthma control. A true-positive case was defined as an exhaled nitric oxide fraction (FeNO) change of less than or the same as a cut-off value (e.g. -25%) associated with an improvement of asthma control between consecutive visits. When smoking patients were treated with a high ICS dose, FeNO lost its ability to assess a control improvement (p = 0.07).