A single blood eosinophil measurement may not be adequate for determining whether an asthma patient can have elevated blood eosinophils.
James Kreindler, MD
Current research is severely lacking in the area of peripheral blood eosinophil shifts in severe asthma.
Although eosinophil counts from sputum provide the most reliable means of diagnosing eosinophilic asthma, the sampling procedure is unsuitable for routine use in a clinical setting, according to a recent study.
Investigators, led by James Kreindler, MD, of the Perelman School of Medicine, University of Pennsylvania, explained that peripheral blood eosinophil counts are commonly viable surrogates for sputum counts. As such, they are commonly used as criteria in the analysis of drugs targeting eosinophils in the treatment of patients with severe, uncontrolled, eosinophilic asthma.
While the degree to which peripheral blood eosinophil counts vary within a single patient has been studied in individuals with mild-to-moderate asthma, blood eosinophil counts are not well understood for those with severe asthma. Investigators sought to provide greater clarity on peripheral blood eosinophil counts associated with events such as exacerbations or responsiveness to biologics in severe asthma.
The study, which analyzed shifts in in blood eosinophil counts for patients with severe, uncontrolled asthma who received placebo during 48-week or 56-week clinical trials, concluded that a single blood eosinophil measurement may not be adequate for determining whether an asthma patient can have elevated blood eosinophils.
Researchers evaluated blood eosinophil shifts in patients randomized to placebo in 2 phase 3 studies, SIROCCO and CALIMA. Results showed that benralizumab significantly reduced exacerbations, improved lung function, and reduced asthma symptoms for patients with severe, uncontrolled asthma despite use of high-dosage inhaled corticosteroids/long-acting beta-2 agonists (LABA) and baseline blood eosinophil counts ≥300 cells/μL, investigators observed.
“Data from the placebo arms of the SIROCCO and CALIMA trials provide an opportunity to examine blood eosinophil counts over time for patients with severe, uncontrolled asthma,” they wrote.
Researchers grouped patients by baseline peripheral blood eosinophil counts and counted the number in each baseline group who had ≥1 recorded peripheral blood eosinophil counts and who then shifted the peripheral blood eosinophil count group during the trial.
Results showed that approximately 70% of patients receiving a placebo with baseline blood eosinophil counts <150 cells/μL had at least one post-baseline blood eosinophil count ≥150 cells/μL during SIROCCO or CALIMA. Approximately one-third had at least 1 post-baseline blood eosinophil count ≥300 cells/μL.
Additionally, approximately 60% of patients with baseline blood eosinophil counts ≥150—<300 cells/μL receiving placebo had at least 1 post-baseline eosinophil count ≥300 cells/μL, according to the study.
While the data concluded that a single blood eosinophil measurement may not be adequate for determining whether an asthma patient can have elevated blood eosinophils, investigators did not postulate whether multiple measurements would be sufficient. As such, additional research may be required to determine whether an asthma patient can have elevated blood eosinophils.
The study, “Peripheral Blood Eosinophil Shifts in Severe, Uncontrolled Asthma,” was published online in the Annals of Allergy, Asthma & Immunology.