Prevalence of eosinophilia in hospitalized patients with asthma exacerbation.

Background: Recent studies have identified the "eosinophilic phenotype" of asthma that is characterized by persistent eosinophilic inflammation and frequent exacerbations. However, the prevalence of eosinophilia in patients hospitalized for asthma exacerbation is not known.

Methods: We performed a pilot study in two sites participating in a multicenter chart review project of children and adults hospitalized for asthma exacerbation during 2012-2013. The pilot study investigated the prevalence of blood eosinophilia in this patient population. Eosinophilia was defined as a count of ≥300 cells/microliter at some time during the hospitalization.

Results: Among 80 patients hospitalized for asthma exacerbation, 47 (59%) underwent CBC with differential and had data on blood eosinophil count. These 47 comprised the analytic cohort. The median patient age was 32 years (IQR, 24-44 years), and 51% were female. Overall, 40% (95% CI, 26%-56%) of patients had eosinophilia. Although statistical power was limited, there were no statistically significant differences in patient characteristics or hospital course between patients with eosinophilia and those without (all P > 0.05).

Conclusion: Our pilot study showed that 40% of patients hospitalized for asthma exacerbation had eosinophilia. The clinical meaning of this biomarker in the emergency department/inpatient setting requires further study in much larger samples with long-term follow-up; such studies appear feasible.