International Variation in Severe Exacerbation Rates in Patients With Severe Asthma

Abstract

BackgroundExacerbation frequency strongly influences treatment choices in patients with severe asthma. Research QuestionWhat is the extent of the variability of exacerbations rate across countries and its implications in disease management? Study Design and MethodsWe retrieved data from the International Severe Asthma Registry, an international observational cohort of patients with a clinical diagnosis of severe asthma. We identified patients aged ≥18 years who did not initiate any biologics prior to baseline visit. A severe exacerbation was defined as the use of oral corticosteroids for ≥3 days or asthma-related hospitalization/emergency room visit. A series of negative binomial models were applied to estimate country-specific severe exacerbation rates during 365 days of follow-up, starting from a naïve model with country as the only variable, to an adjusted model with country as a random-effect term and patient and disease characteristics as independent variables. ResultsThe final sample included 7,510 patients from 17 countries (56% from the United States), contributing to 1,939 severe exacerbations (0.27/person-year). There was large between-country variation in observed severe exacerbation rate (min: 0.04 [Argentina], max:0.88 [Saudi Arabia], interquartile range [IQR]: 0.13–0.54), which remained substantial after adjusting for patient characteristics and sampling variability (IQR: 0.16–0.39). InterpretationIndividuals with similar patient characteristics but coming from different jurisdictions have varied severe exacerbation risks, even after controlling for patient and disease characteristics. This suggests unknown patient factors or system-level variations at play. Disease management guidelines should recognize such between-country variability. Risk prediction models that are calibrated for each jurisdiction will be needed to optimize treatment strategies. Clinical Trial Registration NumberN/A