Difficult/therapy‐resistant asthmaThe need for an integrated approach to define clinical phenotypes, evaluate risk factors, understand pathophysiology and find novel therapies

A Task Force supported by the European Respiratory Society was set up in 1997 in order to address the major issues relevant to difficult/therapy-resistant asthma.Although the group of patients involved is small in comparison to the high numbers of patients with asthma, these patients consume a significant proportion of medical resources in terms of both time and money [1].The major issues facing the Task Force were how to define "difficult asthma", how the patient with difficult asthma should be evaluated, the pathophysiological mechanisms underlying difficult asthma and the treatments available.The Task Force also concerned itself with defining the areas of research necessary to bring about a greater understanding of the causes of difficult asthma and novel treatments.The document resulting from this Task Force represents a consensus of different opinions, which will form the basis for further research. Formulating the definitionA large number of terms are used by clinicians when referring to asthmatic patients who have "difficult to treat" disease: difficult acute, difficult chronic, chronic severe, acute severe, therapy-resistant, difficult to control, corticosteroid-resistant or corticosteroid-dependent, symptomatic, life-threatening, and fatal.An encompassing inclusive rather than exclusive definition was sought and the use of the term "difficult/therapy-resistant asthma" was adopted to include all such cases of asthma of all age groups.Since wheezing disorders in preschool children are poorly characterized, this report specifically excludes children below the age of 5 yrs.Response to therapy is included in this concept and will have research implications.It was accepted that the definition needed to be inclusive, although losing some precision, but it was also recognized that its