A Longitudinal Study of Exhaled Nitric Oxide in Children (LENOS)

Five percent of children in the UK are prescribed steroid inhalers to control asthma symptoms but there is no test to determine whether the dose of steroids is correct. Too much steroid treatment has potential side effects and too little may lead to asthma attacks. Exhaled nitric oxide (ENO) is a gas present in everyone's breath and may be a useful "meter" for asthma control. In children, ENO can be measured easily and quickly, the results are available immediately to the doctor or nurse and for these reasons ENO is an attractive clinical test.

Pioneering studies have used ENO to help clinicians treat asthmatic adults and children and the results are promising. Breathing tests improved among those where asthma treatment was guided by ENO and asthma symptoms were slightly less frequent. These studies all used a single ENO value to increase or reduce treatment and study authors have suggested there should be a range of ENO values where treatment is neither increased nor reduced; what is not known is what these ENO values may be. Elevated NO is associated with a number of factors other than asthma, including allergy and pollen exposure. What is not known is how factors other than asthma affect ENO measurements over time.

The proposed study will answer two important questions: What values of ENO indicate that steroid treatment should be increased or reduced? And how much does ENO rise and fall normally? The investigators will recruit 200 asthmatic and non-asthmatic children. The investigators will measure ENO on six occasions over a 12-month period. The investigators will measure factors that may affect ENO other than asthma. For the asthmatic children, the investigators will also assess asthma control. The investigators' methodology is based on several years experience with ENO. The investigators' results will allow ENO to be used to monitor asthma.