Relationship between exhaled nitric oxide levels and compliance with inhaled corticosteroids in asthmatic children.

Levels of exhaled nitric oxide (eNO) are elevated in subjects with asthma and fall in response to oral or inhaled steroids. This study explored the possibility the measurement of eNO levels could be used to identify subjects who were not adhering to their treatment regimen. Twenty children with asthma attending the respiratory clinic were recruited. Each attended on four occasions 1 month apart when eNO levels were measured. A data logger attached to a pressurised metered dose inhaler was used to objectively monitor use of inhaled corticosteroids (ICSs). The correlation between day and dose compliance with eNO was assessed. The data demonstrated a weak but non-significant correlation between eNO and both day (r = 0.055, P = 0.67) and dose (r = 0.153, P = 0.23). A recorded value of eNO less than 12 was associated with day compliance rates of 3-97%. Of the 19 recorded eNO values greater than 12 ppb almost 80% were from subjects with a day compliance of less than 50% during the preceding month. Of the four values greater than 12 ppb and day compliance > 60% one subject had a poor inhaler technique, one had a mild viral exacerbation and one appeared to be associated with increase pollen exposure. The measurement of eNO may prove to be a useful tool in helping to manage children with asthma but further work is required to define its precise role. Elevated eNO levels in asthmatic children taking ICSs are likely to reflect poor compliance but confounding factors such as disease activity and inhaler technique need to be carefully considered.