Prevalence and cost implications of broadening asthma biologic eligibility criteria

Rationale Eligibility for biologic therapy in severe asthma varies internationally because government-funded schemes apply stricter criteria than pivotal trials. While relaxing eligibility thresholds may expand access, the effects on prevalence and healthcare costs remain uncertain. Objective To quantify how alternative biologic eligibility criteria affect prevalence, clinical characteristics, and budget impact in adults with asthma. Methods We studied adults with active asthma (2004–2021) using nationally representative primary care and hospital records. Biologic eligibility was assessed yearly using asthma severity (inhaled corticosteroid dose, additional controllers, rescue therapy) and exacerbations (oral corticosteroid prescriptions, emergency visits and hospitalisations). We assessed prevalence using United Kingdom (UK) criteria (severe asthma, ≥3 exacerbations), Global criteria (severe asthma, ≥1 or ≥2 exacerbations) and RCT criteria (moderate asthma, ≥1 or ≥2 exacerbations). Anti-IL-5/5Rα eligibility was evaluated using blood eosinophil counts. Budget impact was modelled over 5 years. Results Among 1,306,307 asthma patients, 7.2% had severe asthma. Under UK criteria, 19,093 patients were biologic-eligible (20.4% of severe asthma; 1.5% of all asthma). Global criteria increased eligibility to 2.4% (≥2 exacerbations) to 4.3% (≥1 exacerbation), while RCT criteria expanded eligibility to 4.7% (≥2 exacerbations) and 9% (≥1 exacerbation). Among patients with eosinophil data, 38–45% met anti-IL-5/5Rα criteria. UK-eligible patients had higher prevalence of lower respiratory tract infections, pneumonia, and bronchiectasis. Five-year costs were £261 M under UK criteria, £436–767 M under Global criteria, and £878M-1.6B under RCT criteria. Conclusion Only one-fifth of patients with severe asthma met UK biologic eligibility. Global criteria tripled eligibility and RCT criteria increased it six-fold, with substantial budget implications.