Effect of clinically significant thresholds of eosinophil elevation on health care resource use in asthma.

Background: Blood eosinophil counts correlate with exacerbations, but there is a lack of consensus on a clinically relevant definition of eosinophil count elevation.

Objective: To analyze health care resource use among patients with elevated blood eosinophil counts defined at 150 cells/μL or greater and 300 cells/μL or greater.

Methods: Data on patients who received a diagnosis of asthma between 2007 and 2016 were extracted from EMRClaims + database. Patients were defined as having elevated eosinophil counts if any test result during 3 months before follow-up found blood eosinophil count of 150 cells/μL or more or 300 cells/μL or more. Hospitalizations, emergency department visits, outpatient visits, and associated costs were compared. With logistic regression, likelihood of hospitalization was assessed in the presence of eosinophil elevation.

Results: Among 3687 patients who met the study criteria, 1152 received a test within 3 months before the follow-up period, of whom 644 (56%) had elevated eosinophil counts of 150 cells/μL or greater and 322 (29%) had eosinophil counts of 300 cells/μL or greater. Overall, the mean (SD) number of hospitalizations for patients with elevated eosinophil counts vs the comparator was significantly greater (0.29 [0.92] vs 0.17 [0.57], P < .001 at ≥150 cells/μL and 0.30 [0.95] vs 0.18 [0.61] at ≥300 cells/μL, P = .001). The total mean cost was significantly greater for patients with elevated eosinophil counts (at ≥150 cells/μL: $10,262 vs $7149, P < .001 and at ≥300 cells/μL: $9966 vs $7468, P = .003).

Conclusion: Patients with asthma incurred greater health care resource use when their blood eosinophil counts were elevated at 150 cells/μL or greater and 300 cells/μL or greater as measured within 3 months of follow-up.