Data are presented as %, unless otherwise indicated. PPV: positive predictive value; NPV: negative predictive value. ^#: cut-off value of +30%; ^¶: inhaled corticosteroid (ICS) dose (D) in μg equivalents of beclomethasone diproprionate·day⁻¹; ⁺: ACQ <2 tested the subgroup with an initial ACQ score <2; ^§: ΔD 0 tested the subgroup without treatment modification between consecutive visits; ^ƒ: the p-value is the statistical significance of rejecting an area under the curve of 0.5. A positive event is defined as a worsening of asthma control. 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 worsening of asthma control between consecutive visits. When smoking patients were treated with a high ICS dose, F_eNO ability to detect a worsening of control was somewhat reduced (p = 0.037).