Surrogate markers of airway inflammation: inflammometry in paediatric respiratory medicine.

Until recently, there has not been any practical way to assess airway inflammation non-invasively in paediatrics. Surrogate markers of airway inflammation are potentially of great importance in the diagnosis and monitoring of inflammatory airways disease in children. A large number of substances in blood, urine and exhaled air or induced sputum are currently under study to evaluate their possible usefulness as markers of airway inflammation. To be useful, a marker should be valid, preferably non-invasive, quick, reproducible, repeatable and cheap. In addition, markers should be studied in relation to their specific purpose because different markers may be useful for different types of airway inflammation. Few, if any, markers will fulfill all these requirements. Most research has focused on applications of markers in asthma, some data refer to cystic fibrosis, infections and ciliary dyskinesia. Of all surrogate markers, exhaled nitric oxide has been studied the most and seems to offer information that should be evaluated for its relevance to clinical practice. Before introducing markers of inflammation into daily practice, analysis of benefits and costs are needed. There is little doubt that 'inflammometry' will be a major step forward and will be useful in differentiating airways diseases and improving treatment.