S58 Fev1 and feno as predictors of asthma outcomes in children? an individual patient data analysis using data from six feno trials

Introduction Some guidelines advocate using FEV1 and/or fractional exhaled nitric oxide (FeNO) in the management of childhood asthma, but evidence supporting these recommendations is generally unsupportive. Our hypothesis was that reduced FEV1 and/or elevated FeNO measurements were associated with increased risk of future asthma attacks and loss of asthma control. Methods Data were obtained from six trials where FeNO was used to guide asthma treatment. Baseline% FEV1 and FeNO were linked to exacerbation and loss of control between baseline and three months. Change in% FEV1 and% change in FeNO between baseline and 3 months were also linked to exacerbation and loss of control between three and six months after baseline. A one-stage individual patient data meta-analysis was conducted using a random effect for study. Baseline confounders included in the model were age, sex, LABA, LTRA, ICS dose, trial arm, control and FeNO or FEV1 as appropriate. Results Data were available in 1049 children (58% male, mean age 12.7 years) from six trials. Each unit reduction in baseline% FEV1 was associated with increased risk for future exacerbation (OR 1.02 [1.00, 1.03] n=935, p=0.034) and with increased risk for loss of control (1.01 [1.00, 1.02], n=940, p=0.026) after three months. Similar associations were present between change in%FEV1 and outcomes after six months. Baseline FeNO was not related to asthma outcomes but each 10% increase in FeNO between baseline and three months was associated with increased risk for loss of asthma control by six months (OR 1.02 [1.01, 1.03], n=725, p=0.009) but not with asthma exacerbation. Falling% FEV1 and rising% FeNO between baseline and three months were independently associated with loss of control at six months. Conclusions Baseline% FEV1 is rather weakly associated with future asthma outcomes, and change in%FEV1 between visits does not strengthen this association. In contrast, baseline FeNO is not related to future outcomes but% change in FeNO has some precision for future asthma control. The utility of%FEV1 and FeNO in childhood asthma management needs to be rigorously evaluated in a clinical trial.