Elevated blood eosinophil level and costs for adults with persistent asthma

Background: We examined whether elevated blood eosinophil (eos) level, which is linked to increased asthma exacerbations, is also related to increased all-cause and asthma-related costs. Methods: In this cohort study using administrative pharmacy and health care utilization data, we identified 2392 patients aged 18–64 years with persistent asthma and a blood eos determination in the baseline year. All-cause costs included hospitalization, emergency department (ED) and outpatient (OP) visits, laboratory, radiology, and asthma medications. Asthma-related costs included hospitalizations and ED visits with principal diagnosis of asthma, asthma-related OP visits, laboratory and radiology, and asthma medications. The relationship of baseline blood eos level to all-cause and asthma-related costs in the follow-up year was estimated by generalized linear models with gamma distribution, adjusted for demographics, comorbidities, prior exacerbation, step-care treatment, and baseline costs. Results: Greater blood eos counts at baseline were associated with increased total asthma-related costs, but not all-cause costs. The adjusted incremental increases in asthma-related costs were $377 (400 cells/μL cutoff) and $237 (300 cells/μL cutoff). Conclusions: Elevated blood eos count is an independent risk factor for increased asthma-related, but not all-cause costs for adults with persistent asthma, confirming the importance of blood eos in this group.