1. The patient is unable to perform acceptable spirometry, peak flow measurements and/or complete diary cards in a satisfactory way during the period between visit 1 and visit 3B (optimisation period and prednisolone/placebo trial). If the patient is unable to use the electronic Peak Flow meters/Diary cards, it is acceptable to use an ordinary mechanical meter (e.g. Mini-Wright) together with a paper version of the diary card. Patients that are unable to use the mechanical meter and paper diary card during the period between visit 1 and 3B cannot enter the follow-up year.