Elevated Blood Eosinophil Levels Are a Risk Factor for Asthma Exacerbations

Published Online: August 29, 2014

Eosinophilic inflammation hallmarks several asthma phenotypes, and high blood eosinophil counts appear to be associated with uncontrolled asthma. However, it is not known whether results of blood eosinophil counts will help to identify persistent asthmatics at increased risk for future asthma exacerbations in asthma population care management. In an article recently published in The Journal of Allergy and Clinical Immunology: In Practice, Zeiger and colleagues determined whether blood eosinophil count is a risk factor for future asthma exacerbations in adult persistent asthma.

The investigators used electronic pharmacy/healthcare data from Kaiser Permanente Southern California to identify 2,392 patients aged 18-64 years who met the Health Effectiveness Data and Information Set (HEDIS) 2-year criteria for persistent asthma, did not manifest chronic obstructive pulmonary disease or other major illnesses, and had a blood eosinophil determination in 2010. Exacerbations (primary outcome) were defined as asthma outpatient visits requiring systemic corticosteroid dispensing within +7 days or asthma emergency department visits or hospitalizations. A period of >8 days defined a new exacerbation. Multivariate modeling examined the association between blood eosinophil count determined in 2010 and risk of exacerbations, and >7 short-acting b2-agonist (SABA) canisters dispensed (secondary outcome of excessive SABA dispensings) in 2011, adjusting for demographics, comorbidities, and asthma burden.

Zeiger, et al. found that higher numbers of blood eosinophils in 2010 was significantly associated with increasing risk of future asthma exacerbations in 2011 in both unadjusted and adjusted analyses. In the population studied, an eosinophil count >400/mm3 in 2010 was associated with a 31% increase in asthma exacerbations and a 17% increase in excessive SABA canisters dispensed in 2011, after adjustment for multiple variables. Other factors in 2010 that were significantly associated with an increased risk of exacerbations in 2011 included a history of prior asthma exacerbations, Global Initiative for Asthma (GINA) steps-4/5 care, dispensing of 7 or more SABA canisters, female gender, black ethnicity, and obesity.

The investigators concluded that high blood eosinophil counts in adults with persistent asthma were associated with increased future asthma risk (exacerbations) and excessive SABA use (impairment) in a large Managed Care Organization administrative database study. Population care management programs and clinical practice should consider measurement of blood eosinophil count as an additional biological marker to assist in the identification of persistent adult asthma patients with higher risk for future exacerbations and excessive SABA use.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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