Usefulness of monitoring lung function in asthma.

There is no firm evidence from randomised controlled trials that routine monitoring of lung function improves asthma control in children. Guidelines for management of asthma consistently recommend routine home monitoring of peak expiratory flow (PEF) in each patient. However, changes in PEF poorly reflect changes in asthma activity, PEF diaries are kept very unreliably, and self management programmes including PEF monitoring are no more effective than programmes solely based on education and symptom monitoring. PEF diaries may still be useful in isolated cases of diagnostic uncertainty, in the identification of exacerbating factors, and in the rare case of children perceiving airways obstruction poorly and exacerbating frequently and severely. If a reliable assessment of airways obstruction in asthma is needed, forced expiratory flow-volume curves are the preferred method. Monitoring of hyperresponsiveness and nitric oxide cannot be recommended for routine use at present. Clinical judgement and expiratory flow-volume loops remain the cornerstone of monitoring asthma in secondary care.