Prevalence and burden of difficult‐to‐treat and severe asthma in Australia: A national population survey.

Background and Objective: Most evidence about difficult‐to‐treat and severe asthma (DTTA) comes from clinical trials and registries. We aimed to identify people with DTTA from a large nationally representative asthma population and describe their characteristics and healthcare utilization compared with people whose asthma was not 'difficult‐to‐treat'. Methods: We conducted a cross‐sectional survey of Australians aged ≥18 years with current asthma from large web‐based survey panels. Enrolment was stratified by gender, age‐group and state/territory based on national population data for people with asthma. Difficult‐to‐treat or severe asthma was defined by poor symptom control, exacerbations and/or oral corticosteroid/biologic use despite medium/high‐dose inhaled therapy. Outcomes included exacerbations, healthcare utilization, multimorbidity, quality of life and coronavirus disease of 2019 (COVID‐19)‐related behaviour. Weighted data were analysed using SAS version 9.4. Results: The survey was conducted in February–March 2021. The weighted sample comprised 6048 adults with current asthma (average age 47.3 ± SD 18.1 years, 59.9% female), with 1313 (21.7%) satisfying ≥1 DTTA criteria. Of these, 50.4% had very poorly controlled symptoms (Asthma Control Test ≤15), 36.2% were current smokers, and 85.4% had ≥1 additional chronic condition, most commonly anxiety/depression. More than twice as many participants with DTTA versus non‐DTTA had ≥1 urgent general practitioner (GP) visit (61.4% vs. 27.5%, OR 4.8 [4.2–5.5, p < 0.0001]), or ≥1 emergency room visit (41.9% vs. 17.9%, OR 3.8 [3.3–4.4, p < 0.0001]) in the previous 12 months. Conclusion: Our findings emphasize the burden of uncontrolled symptoms, current smoking, multimorbidity and healthcare utilization in people with DTTA in the community, who may be under‐represented in registries or clinical trials. In this cross‐sectional study of a nationally‐representative population of 6048 adults with current asthma, 21.7% had difficult‐to‐treat asthma. Burden for patients and health system was seen in poor general health status, poor asthma symptom control, frequent urgent GP and emergency department (ED)/hospital visits and high prevalence of multimorbidity, particularly anxiety and/or depression. See relatededitorial [ABSTRACT FROM AUTHOR]