• Relative risk reduction for the occurence of the first exacerbation and the length of time without exacerbation during Phase 2 of the study.
  

• Secondary outcomes were
  
• The cellular type of exacerbation that was influenced,
  
• The severity of asthma that was helped,
  
• The dose of inhaled corticosteroid that was required,
  
• Symptom control,
  
• Quality of life,
  
• FEV1
  
• Methacholine PC20,
  
• Exhaled NO,
  
• Cost effectiveness and cost benefit of sputum cell counts, Airway structural changes
  
• Skin bruising score.
  

Airway inflammation is an important component of asthma. It influences other components which include symptoms and airway functional (physiological) measurements. It is the primary target of treatment. However, it does not correlate closely with symptoms, need for symptomatic bronchodilator relief, or the physiological abnormalities. Furthermore, it can be of different types. As a result, physicians are poor at recognizing its presence or type. This is important because eosinophilic inflammation is responsive to corticosteroid while non-eosinophilic is not responsive.

The most comprehensive non-invasive or relatively non-invasive measurement of airway inflammation is by spontaneous or induced sputum cell counts. These are reliable, valid and responsive, the qualities of good measurements. They might therefore be clinically useful to guide individual treatment. In the present study we investigated this issue. We compared their use, in comparison with the use only of symptoms and spirometry, in preventing exacerbations of asthma. We chose prevention of exacerbations as the most important clinical outcome because these have the greatest impact on patient’s quality of life, morbidity and healthcare utilization. The study comprised two Phases. In Phase 1, the minimum treatment to control sputum eosinophilia (as well as clinical criteria) in the Sputum Strategy, and clinical criteria in the Clinical Strategy, were established. In Phase 2, this minimum treatment was maintained and patients were seen every 3 momths and at exacerbations. The primary outcomes were the relative risk reduction for the occurrence of the first exacerbation and the length of time without exacerbation over 18-20 months in Phase 2 of the study.