The purpose of this study was to determine whether the use of induced sputum cell counts could guide treatment of asthma more effectively than the use of symptoms and breathing tests. The main outcomes where the time to the first exacerbation and the number of exacerbations.

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.

Inclusion Criteria:

1. History of asthma for at least one year,confirmed objectively.
2. New or previously reviewed patients where the minimal treatment requirements have not been established within the last six months.

Exclusion Criteria:

1. Smokers or ex-smokers for less than 6 months with a smoking history of more than 10 pack years.
2. Other pulmonary co-morbidity (other than mild or moderate chronic airflow limitation).
3. Subjects having a co-existing illness that precludes them from the study.
4. Inability to give informed consent due to mental or legal reasons.
5. Pregnancy or lactation.
6. Known non-compliance with medications.