GRADE Working Group grades of evidence.

High quality: further research is very unlikely to change our confidence in the estimate of effect.

Moderate quality: further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.

Low quality: further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.

Very low quality: we are very uncertain about the estimate.

^*The basis for the assumed risk (eg, the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% CI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).

1 CIs are wide and include clinically important benefit and harm.

2 One study (deJongste 2008) design was open label which may have introduced bias.

3 Studies reported technical difficulties with FeNO analyses as reported in risk of bias table.

4 Medication increased prior to commencement of study.

5 In one study the overall dose of ICS was higher with FeNO-based interventions even though the final ICS dose was lower.

6 One study presented in these results was single blinded with the intervention arm analysing FeNO only.

7 Final ICS doses were quite varied, with one study having particularly high doses.

FeNO, fractional expired nitric oxide; ICS, inhaled corticosteroid.