| First author [ref.] | Definition of exacerbation |
| Murphy [7] | Hospital admission, emergency department presentation, unscheduled doctor's visit or course of OCS |
| Stenius-Aarniala [6] | Not controlled by the patient's normal rescue medication and which was treated as an emergency (74.4% OCS) |
| Jana [12] | Requiring emergency services and/or hospitalisation |
| Schatz [17] | Requiring emergency therapy with nebulised bronchodilators in the clinic or emergency room |
| Greenberger [16] | Requiring adrenaline and OCS in the outpatient service, emergency room or hospital |
OCS: oral corticosteroids.