Differentiation of adult severe asthma from difficult-to-treat asthma – Outcomes of a systematic assessment protocol

Abstract Background Guidelines recommend a differentiation of difficult-to-treat asthma from severe asthma. However, this might be complex and to which extent this distinction is achievable in clinical practice remains unknown. Objective To evaluate to which degree a systematic evaluation protocol enables a differentiation between severe versus difficult-to-treat asthma in patients in specialist care on high intensity asthma treatment, i.e. potentially severe asthma. Methods All adult asthma patients seen in four respiratory clinics over one year were screened prospectively for asthma severity. Patients with difficult-to-control asthma according to ERS/ATS criteria (high–dose inhaled corticosteroids/oral corticosteroids) underwent systematic assessment to differentiate severe asthma patients from those with other causes of poor asthma control: objective confirmation of the asthma diagnosis as well as assessment of treatment barriers and comorbidities. Results Overall, 1034 asthma patients were screened, of whom 175 (16.9%) had difficult-to-control asthma. 117 of these accepted inclusion, and completed systematic assessment. Asthma diagnosis was objectively confirmed in 88%. Sub-optimal adherence (42.5%), inhaler errors (31.5%) and unmanaged comorbidities (66.7%) were common. After primary assessment, 12% (14/117) fulfilled strict criteria for severe asthma. Moreover, 56% (66/117) were instantly classified as difficult-to-treat asthma due to poor adherence/inhaler technique. Finally, an ´overlap' group of 32% (37/117) were identified with patients being adherent and displaying correct inhaler technique, but had unmanaged comorbidities —potentially fitting into both the difficult-to-treat and severe group. Conclusion Only a minority of patients with difficult-to-control asthma were found to have severe asthma after primary systematic assessment. Nevertheless, strict categorisation of severe vs. difficult-to-treat asthma seems to pose a challenge.