One request thought the British Columbia ministry of health (personal communication with Data Stewardship Secretariat) is required to retrieve data on the study participants as well as cases of asthma across the entire province, without additional cost for the latter group. The investigators will use this opportunity to retrieve data on cases of asthma in the entire province and compare different aspects of resource utilization between objectively verified cases of asthma and the data retrieved using a case definition algorithm on an administrative database. Such data will be used to retrospectively estimate the direct costs of asthma during the follow-up and in the 12 months prior to the enrolment in the study. The direct medical costs calculated in this way will be compared with the direct costs calculated in the prospective phase of the study. In addition, the investigators will examine the representativeness of the sample population by comparing the participant's health records with case of asthma in British Columbia identified through the BC Linked Health Database. Given the objective validation of the diagnosis of asthma at the end of the follow-up period in Phase A, the investigators will also be able to explore the sensitivity of existing case ascertainment algorithms based on administrative data at levels of severity and control.