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Forest plot comparing the number of participants in randomised clinical trials who had an asthma attack requiring treatment with oral steroids. Participants were randomised to asthma treatment guided by fractional exhaled nitric oxide plus standard care (symptoms±forced expiratory volume in 1 s) or standard care only. RAACENO: Reducing Asthma Attacks in Children Using Exhaled Nitric Oxide; M–H: Maentel–Haenszel; df: degrees of freedom.
