Response

To the Editor: We thank Drs Yawn and Kaplan for their interest and comments on our article in which we describe a secondary analysis of data from seven published trials where fractional exhaled nitric oxide (Feno) was used to guide asthma treatment in children.1 We believe that our results offer relevance to clinicians attempting to interpret repeated measurements of spirometry and Feno. To the best of our knowledge, our analysis is the first to: (1) compare the clinical outcomes following a change in FEV1 and Feno over time; (2) compare clinical outcomes following absolute vs percent change in Feno; and (3) describe clinical outcomes following changes in FEV1 that fall within the range of “normal.”