Eosinophilia worsens asthma exacerbation severity
medwireNews: Eosinophilic asthma exacerbations identify patients with a severe disease course who could benefit from specific interventions, researchers report.
Eosinophilic asthma exacerbations were identified in 16 (43%) of 37 patients aged 16–45 years who presented to hospital and had sputum successfully induced that showed eosinophil levels of 3% or above.
These individuals had significantly lower forced expiratory volume in 1 second (FEV1) % predicted in the 24 hours following hospital admission, at 70.8%, compared with 83.6% for the remaining 21 patients with non-eosinophilic exacerbations (p=0.03).
The difference in FEV1 remained significant after taking into account smoking and the use of inhaled corticosteroids.
The need for oxygen supplementation was also significant greater among patients with eosinophilic asthma exacerbations and was given to 63% of these patients, compared with 14% of those with non-eosinophilic exacerbations.
Airway eosinophils continued to be elevated 4 weeks later in just over half of patients with an eosinophilic exacerbation, despite treatment with systemic steroids.
The prevalence of respiratory viruses and bacterial infections was the same for both groups and did not explain the findings.
“The patients with eosinophilia at follow-up could represent an underlying phenotype with an increased risk of future exacerbations,” says the team led by Asger Bjerregaard (Bispebjerg University Hospital, Copenhagen, Denmark), although they note that further clarification is needed.
The percentage of sputum eosinophils correlated significantly with fractional expiratory nitric oxide (FeNO), providing a potential biomarker. Indeed, at a cutoff of 25 ppb, FeNO predicted airway eosinophilia with 86% sensitivity and 70% specificity. Blood eosinophils also correlated with sputum eosinophils but were less predictive.
The researchers conclude in Respirology: “Our findings add to the limited data available on eosinophilia during acute asthma and suggest that the new biological treatment options that are becoming available may have an attenuating effect on exacerbations.”
Anti-interleukin-5 treatments, for instance, reduce the rate of exacerbations by upwards of 50% in some asthma patients with substantial eosinophilia and frequent exacerbations, the team reports; and may therefore also be beneficial for patients with a predominantly eosinophilic inflammatory response, the authors suggest.
By Lucy Piper
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