Change in FEV₁ and FeNO measurements as predictors of future asthma outcomes in children

Background
Repeated measurements of spirometry and fractional exhaled nitric oxide (FeNO) are recommended as part of the management of childhood asthma, but the evidence base for such recommendations is small. We tested the hypothesis that reducing spirometric indices or increasing FeNO will predict poor future asthma outcomes.

Methods
A one-stage individual patient data meta-analysis used data from seven randomised controlled trials where FeNO was used to guide asthma treatment, and where spirometric indices were also measured. Change in %FEV1 and % change in FeNO between baseline and three months were related to having poor asthma control and to having an asthma exacerbation between three and six months after baseline.

Results
Data were available from 1112 children (mean age 12.6 years, mean %FEV1 94%). A 10% reduction in %FEV1 between baseline and three months was associated with 28% increased odds for asthma exacerbation [95% CI 3, 58] and with 21% increased odds for having poor asthma control [95% CI 1, 45] six months after baseline. A 50% increase in FeNO between baseline and three months was associated with 11% increase in odds for poor asthma control six months after baseline [95% CI 0, 16]. Baseline FeNO and %FEV1 were not related to asthma outcomes at three months.

Conclusions
Repeated measurements of %FEV1 which are typically within the “normal” range add to clinical risk assessment of future asthma outcomes in children. The role of repeated FeNO measurements is less certain since large changes were associated with small changes in outcome risk.