Blood eosinophil levels may present significant variability throughout the course of chronic obstructive pulmonary disease (COPD), which means that a single measurement may not be a reliable treatment response, according to study results published in the journal CHEST.
Blood samples from patients with stable COPD were obtained to determine the blood eosinophil levels during half-yearly visits when COPD was stable and during unscheduled visits when the patient was having moderate and severe exacerbations. Eosinophil levels were considered to be concordant when they were persistently lower than or persistently higher than the absolute cutoff points of 150 and 300 cells/mL or the percentage cutoff points 2%, 3%, and 4%, respectively. Data were dichotomized according to stable state or exacerbation status, and inhaled corticosteroids use was noted.
Among the 210 participants, 2059 visits were included in the study. Of these 210 participants, 70% were men, 36% were smokers, and 81% were receiving inhaled corticosteroids. The average follow-up time was 4 years. When eosinophil levels were assessed over time, there was a discordance of 77%, 60%, and 42% when using the 2%, 3%, and 4% cutoffs. Of note, patients in a stable state had higher discordant values than patients with mild/moderate exacerbations. Furthermore, the level of discordance was high regardless of whether patients were taking inhaled corticosteroids at the beginning of the study period.
The study authors wrote, “Considering the high percentage of variability in the blood eosinophil levels throughout the time the patients were followed up, it would be difficult to ascertain whether the patients would be responsive to inhaled corticosteroids.” They added, “These data suggest that blood eosinophil levels present significant variability throughout the course of COPD, and a single measurement may therefore not be a reliable predictor of [inhaled corticosteroid] response.”
Schumann DM, Tamm M, Kostikas K, Stolz D. Stability of the blood eosinophilic phenotype in stable and exacerbated COPD. CHEST. 2019;156(3):456-465.