Using fractional exhaled nitric oxide to guide step down treatment decisions in patients with asthma: a systematic review and individual patient data meta-analysis.

Wang K, Verbakel JY, Oke J, Fleming-Nouri A, Brewin J, Roberts N, Harada N, Atsuta R, Takahashi K, Mori K, Fujisawa T, Shirai T, Kawayama T, Inoue H, Lazarus S, Szefler S, Martinez F, Shaw D, Pavord ID, Thomas M