Noninvasive monitoring of airway inflammation.

What we know: Various techniques are available that purport to measure aspects of airway inflammation non-invasively, including analysis of volatile molecules in exhaled breath and components of breath condensates. Adapting and validating these methods for use in young children and infants poses significant methodological problems, but progress has been made, particularly with regard to measurements of exhaled nitric oxide. Future studies to validate such tests are likely to require access to airway tissue for examination as a "gold standard". What we need to know: How can we obtain airway tissue from infants and young children to better characterise the early airway changes in asthma? How do non-invasive tests of airway inflammation compare with a validated gold standard? How sensitive and specific are non-invasive tests of inflammation for predicting outcomes in asthma, including response to therapy?