No the evidence: What have measurements of exhaled nitric oxide got to offer?

The relationship between the measurement of exhaled nitric oxide (FeNO) and pediatric investigators has gone from the heady excitement of the early flirtations to a more solid and permanent relationship, perhaps less superficially exciting, requiring harder work, but ultimately more realistic. The initial nitric oxide studies were largely cross-sectional or, at best, very-short-term longitudinal, but were sufficient to suggest that here was something that added a new dimension to the management of asthma.

Abbreviations:  FeNO, Exhaled nitric oxide