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Eosinophils linked to worsening asthma

Measuring blood levels might help predict exacerbations and direct treatment

Louise Prime

Wednesday, 21 May 2014

Measuring blood eosinophil levels could in future help guide treatment in those people with persistent asthma who are at highest risk of exacerbations, suggest researchers. Their study*, presented this week at the 2014 American Thoracic Society International Conference in San Diego, found that elevated levels of eosinophils in adults with asthma were an independent risk factor for exacerbations.

The researchers used pharmacy and health care records to identify 2,392 people aged 18-64 years with persistent asthma, but no other major illnesses including chronic obstructive lung disease, and who had had a blood eosinophil measurement recorded. They then looked for associations between various risk factors – including patients’ baseline eosinophil level in 2010, prior exacerbations, age, sex, ethnicity, educational status, and number of prescriptions dispensed for short-acting beta-agonists – and their risk of subsequent asthma exacerbation in 2011. They defined an exacerbation as when a patient’s worsening asthma led to a visit to A&E, hospital admission or an outpatient visit requiring systemic corticosteroid dispensing within +7 days.

Having an elevated eosinophil level (>400/mm3) in 2010 was independently associated with patients’ risk of asthma exacerbations in 2011, after adjustment for multiple baseline features (adjusted rate ratio 1.31). The association with an eosinophil level >300/mm3 was less strong (ARR 1.16).

Other factors that significantly increased study participants’ risk of subsequent exacerbations included a history of prior asthma exacerbations, GINA steps-4/5 care, dispensing of seven or more short-acting beta-agonist canisters, female sex, black ethnicity, and obesity.

The authors said: “Eosinophils are known to be involved in the pathophysiology of asthma, and determining their relationship with asthma exacerbations may allow us to determine in advance which of these patients needs targeted interventions. In our study, elevated blood eosinophil levels were found to be a risk factor for subsequent exacerbations in adult asthma patients.”

They said their results suggest a higher disease burden in asthma patients with elevated blood eosinophil, and concluded: “If our findings can be replicated in other populations and settings, measurement of blood eosinophil levels may help guide treatment for patients at the greatest risk for exacerbations.”

* Zeiger R S, Schatzl M, Li Q, Chen W, Khatry D, Tran T N. Elevated Blood Eosinophil Level Is A Risk Factor For Exacerbations In Adult Persistent Asthma. Abstract 50175.

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