The purpose of the present proposal was to investigate the predictive properties of markers in exhaled breath to predict an asthma exacerbation. In addition, the reliability of home monitor assessments to measure asthma control will be examined.

Inclusion Criteria:

1. already known with a diagnosis of asthma during at least 6 months
2. age between 6 and 17 years
3. reversibility to a bronchodilator (increase in FEV1 > 9% of predicted value and/or
4. bronchial hyperresponsiveness to histamine < 8 mg/ml.

Exclusion Criteria:

1. cardiac abnormalities
2. mental retardation, congenital abnormalities or existence of a syndrome
3. active smoking
4. no technical satisfactory performance of measurements
5. no phone line or internet assess available at home.

This study is carried out in two hospitals in the Netherlands (Maastricht University Medical Centre, Maastricht; and Orbis Medical Centre, Sittard).