Association between blood eosinophil counts and risk of rehospitalization in patients with asthma

Introduction: A United Kingdom study (Lancet Respir Med. 2015;3:849–58) demonstrated a greater risk of asthma exacerbations with high blood eosinophil counts (BEC). Aims and Objectives: We aimed to determine if patients hospitalized for asthma exacerbations were more likely to be readmitted if they had high BEC before admission. Methods: We analyzed 2 years of medical records data (Clinical Practice Research Datalink with Hospital Episode Statistics Linkage) from patients (aged ≥5 years) hospitalized for asthma who had BECs recorded within 1 year before admission. Patients were characterized in a baseline year, prior to the most recent first hospitalization for asthma (index date) occurring within 1 year after a BEC recording. We analyzed the association between high BEC (≥0.35 x 109/L) and readmission risk during 1 year of follow-up after index date, with adjustment for age, sex, smoking, and timing of most recent BEC as confounders. Results: A total of 835 of 2,613 patients with asthma (32%) had high BEC. In addition, 130 (55 with high BEC) patients were rehospitalized for asthma during the follow-up year. Patients with prior high BEC had a greater risk (6.6% vs. 4.2%; p=0.009) and a greater hazard ratio (HR: 1.45; 95% CI: 1.02−2.08; p=0.040) of readmission than those without high BEC. The association was strongest for nonsmokers (HR: 1.95; 95% CI: 1.16−3.31; p=0.013), compared with ex-smokers (HR: 1.52; 95% CI: 0.74−3.10; p=0.253) and with current smokers (HR: 0.97; 95% CI: 0.48–1.97; p=0.936). Conclusions: Patients with asthma and preadmission high BEC have a greater risk of rehospitalization for exacerbations.