Airway calibre variation is a major determinant of exhaled nitric oxide's ability to capture asthma control.

Changes in airway calibre have the potential to modify exhaled nitric oxide fraction () values and could hamper how captures changes in asthma control. Here, our objective was to assess whether forced expiratory volume in 1 s (FEV) variations alter the ability of to reflect asthma control., asthma control (Asthma Control Questionnaire (ACQ)) and FEV were measured at least two times in 527 patients during 1819 pairs of visits. Determinants of -ACQ discordance probability were evaluated through a logistic regression analysis. The effectiveness of at capturing either asthma control worsening or improvement between two visits was then assessed by undertaking a stratified receiver operating characteristic curves analysis.When FEV and change in the same direction, the odds of -ACQ being discordant are multiplied by 3 (p<0.001). The area under the curve values were 0.765 (95% CI 0.713-0.805) (improvement; p<0.001) and 0.769 (95% 0.706-0.810) (worsening; p<0.001) or 0.590 (95% 0.531-0.653) (improvement; p=0.001) and 0.498 (95% 0.416-0.567) (worsening; p=0.482) when FEV and changed in the opposite or same direction, respectively.The manner in which and FEV vary concomitantly when asthma control changes determines the ability of to capture this change: parallel or opposite changes in FEV and either decrease or increase this ability to capture asthma control changes.