Comparison of exacerbation phenotypes among patients with severe asthma

Background: Exacerbation phenotypes among patients with severe asthma have been largely characterized during stable periods. Little is known about severe asthma patients during exacerbation periods. Objective: To compare persistently frequent exacerbators (PFE), non-persistently frequent exacerbators (NPFE), and infrequent exacerbators (IFE) among patients with severe asthma during stable and exacerbation periods. Methods: Patients with severe asthma who were admitted for asthma exacerbations from 2011 to 2017 and on follow up at Singapore General Hospital were recruited and categorized as PFEs (two or more exacerbations per year over 2 consecutive years), NPFEs (two or more exacerbations in 1 year only), or IFEs (fewer than two exacerbations per year over 2 consecutive years). Demographic, clinical, and laboratory data were collected at baseline and during exacerbation periods. Results: The participants were categorized as the following: 20 PFEs, 36 NPFEs, and 57 IFEs, with no significant demographic differences. The participants as PFEs (versus NPFEs and IFEs) were characterized by having a higher prevalence of psychiatric disorders (25% versus 8% versus 5%; p = 0.046), more comorbidities (7 versus 4 versus 2; p < 0.001), and a higher steroid burden per year (1150 versus 456 versus 350 mg; p < 0.001). The participants who were PFEs (versus IFEs) had a higher total immunoglobulin E (IgE) level (625 versus 232 IU/mL; p = 0.046) and longer duration of admission stay (3 versus 2 days; p = 0.009). All three groups had higher blood neutrophil counts during exacerbation periods than during stable periods (p = 0.008 versus p < 0.001 versus p = 0.004). Conclusion: The participants categorized as PFEs were characterized by comorbidities, higher steroid burden, IgE levels, and longer hospital stays. Exacerbations in the participants with severe asthma, regardless of exacerbation phenotype, were characterized by neutrophilia. These findings provided insights into potential therapeutic strategies to reduce exacerbations in patients with severe asthma.