Background Repeated measurements of spirometry and fractional exhaled nitric oxide (F eno ) 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 F eno will predict poor future asthma outcomes.

Methods A one-stage individual patient data meta-analysis used data from seven randomized controlled trials in which F eno was used to guide asthma treatment; spirometric indices were also measured. Change in %FEV 1 and % change in F eno between baseline and 3 months were related to having poor asthma control and to having an asthma exacerbation between 3 and 6 months after baseline.

Results Data were available from 1,112 children (mean age, 12.6 years; mean %FEV 1 , 94%). A 10% reduction in %FEV 1 between baseline and 3 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, 0-45) 6 months after baseline. A 50% increase in F eno between baseline and 3 months was associated with 11% increase in odds for poor asthma control 6 months after baseline (95% CI, 0-16). Baseline F eno and %FEV 1 were not related to asthma outcomes at 3 months.

Conclusions Repeated measurements of %FEV 1 that are typically within the “normal” range add to clinical risk assessment of future asthma outcomes in children. The role of repeated F eno measurements is less certain because large changes were associated with small changes in outcome risk.