Blood eosinophil variability in asthma may better identify risk for hospital episodes

Among patients with asthma, blood eosinophil variability resulted in better identification of risk for hospital episodes compared with absolute counting values that are currently used to target specific asthma treatments.

“Despite the important relationship between asthma and eosinophil values, there is not clear evidence about eosinophil distribution in a nonsevere asthma cohort and in the general population in clinical practice or about their cutoff values to predict clinical outcomes or their variability over time,” Nuria Toledo-Pons, MD, from the department of respiratory medicine at the Balearic Islands Health Research Institute in Palma de Mallorca, Spain, and colleagues wrote in Annals of the American Thoracic Society.

Researchers evaluated the distribution and variability of 35,703 eosinophil determinations from 10,059 patients with asthma (mean age, 51.2 years; 31.7% men) in the Majorca Real-Life Investigation in COPD and Asthma cohort. Eosinophil distribution among those with asthma was compared with 8,557 controls without asthma (mean age, 51.5 years; 41.9% men).

Among patients with asthma, the mean blood eosinophil count was 300.8 cells/µL and median blood count was 251 cells/µL.

Researchers reported higher eosinophil count values and variability among patients with asthma compared with controls (251 cells/µL vs. 190 cells/µL; P < .001). Male sex, younger age and type 2 comorbidities were associated with higher eosinophil blood counts in patients with asthma.

In addition, the researchers reported a better association with asthma hospital episodes and eosinophil variability data compared with the eosinophil counting values.

The Eosinophil Variability Index was defined as the proportion of the range to the maximum eosinophil value multiplied by 100% of all eosinophil measurements from each patient and the overall population. An Eosinophil Variability Index of 50% or more was found to be a better predictor for any asthma hospital episode compared with any absolute eosinophil counting values (adjusted OR = 2.58; 95% CI, 2.23-2.97), according to the researchers.

Researchers validated these findings in an external cohort.

“The Eosinophil Variability Index could be an easy and pragmatic instrument to better identify patients at high risk of developing uncontrolled asthma and who could be, in the future, candidates of specific treatments,” the researchers wrote. “Notwithstanding, prospective trials will be needed to completely validate the Eosinophil Variability Index as a predictive tool.”