The main objectives of the study are:

-to unravel the importance of molecular phenotyping in predicting the response to classical anti-asthma treatment (inhaled corticosteroids)

The investigators have developed a non-invasive technique based on mRNA analysis of induced sputum that enables us to study airway inflammation in detail. This technique forms the basis for our current project based on the following hypotheses:

1. different molecular asthma phenotypes exist: a Th2 phenotype and a non Th2 phenotype as reported by Woodruff and colleagues (Woodruff PG et al). Sputum mRNA cytokine levels can be used to diagnose Th2 asthma and discriminate this from non-Th2 asthma.
2. Based on our previous research and preliminary data that non-Th2 asthma can be further divided in Th17 asthma and Th1+Th2 asthma; besides these, a fourth group without Th2, Th17 or Th1 characteristics also exist. The investigators hypothesize that the epithelial cell cytokine, TSLP, can be increased as an early marker of airway inflammation in this latter group.
3. these subgroups have different responses to anti-inflammatory treatment.

Inclusion Criteria:

• steroid naive asthmatics

Exclusion Criteria:

• viral/bacterial/fungal infection +fever(<1month)
• asthma exacerbation (<3months)
• other airway diseases (CF, ciliary dyskinesia, bronchiectasis)