The primary outcomes will be analyzed as total exacerbations during the time frame and as a time-dependent variable (time to exacerbation) using Kaplan Meier survival analysis. Additional sub-analyses will be made for the type of inclusion setting (ED/hospitalization), number of prior exacerbations, and eosinophil count. Additional analyses will be made for all secondary outcomes. Analyses relevant only for the intervention group (such as spirometry and IOS) will compare results to the first follow-up visit. A cost-effectiveness analysis will be made, comparing the follow-up cost and the cost saved by exacerbation reduction based on the final results.
Sample size calculation - The invetigators assume based on previous research that the intervention will lead to a 20% decrease in exacerbations during the 12 months from first follow-up. To achieve an alpha of 0.05 and a power of 80%, there is a need for 88 patients in each group. Assuming a loss-to-follow-up rate (missing to complete at least 2 clinic visits or loss to phone follow-up) of 20%, the study will need 115 patients in each group (230 overall).
