title: Risk factors of frequent exacerbations in difficult-to-treat asthma.
authors.forename: C
authors.initials: C
authors.lastname: Butler
authors.forename: L G
authors.initials: LG
authors.lastname: Heaney
mesh_terms: D018927:Anti-Asthmatic Agents / Q000627:therapeutic use*; D001249:Asthma / Q000188:drug therapy* / Q000453:epidemiology / Q000209:etiology*; D015897:Comorbidity; D003937:Diagnosis, Differential; D006801:Humans; D012008:Recurrence; D012307:Risk Factors; D017211:Treatment Failure; D016312:Treatment Refusal / Q000706:statistics & numerical data
chemical_list: D018927:Anti-Asthmatic Agents