Non-invasive biomarkers of asthma

Several non-invasive biomarkers of inflammation in asthma such as exhaled NO and eosinophil numbers in induced sputum have been developed. Their usefulness in experimental asthma models has been validated but there is less experience in their use in clinical practice. Because specific cooperation may be needed from the patient in producing samples from the airways for assay of biomarkers, younger children may not be suitable. Specific experience in these age groups is required. There remains a need to examine these biomarkers in patients from the mild asymptomatic to the more symptomatic difficult asthmatic in longitudinal studies. Is it useful to monitor these biomarkers as a response to treatment rather than the more conventional measures of symptoms and lung function measurements for prevention of exacerbations and long-term reduction in lung function? Answers to such issues will be crucial in adopting the routine measurement of certain biomarkers from the airways in the assessment of asthma severity and control.