The site of eosinophilic inflammation, whether local, systemic or both, has a significant effect on lung function, bronchial hyperresponsiveness and asthma control, study findings show.
The results suggest that patients with isolated sputum eosinophilic inflammation have impaired lung function and increased bronchial hyperresponsiveness compared with those without eosinophilic inflammation, while having both local and systemic inflammation contributes to further functional impairment and in turn worse asthma control and quality of life.
“This suggests that the global magnitude of eosinophilic inflammation is a significant factor in disease severity,” say lead researcher Florence Schleich (CHU Sart-Tilman, Liege, Belgium) and colleagues.
Asthma severity in patients with isolated systemic eosinophilic inflammation was no worse than that in patients without eosinophilic inflammation.
Patients with concomitant local and systemic inflammation, according to sputum (at least 3%) and blood (at least 400 cells per mm3) eosinophils, respectively, made up 19% of a retrospective cohort of 508 participants with asthma, while asthma patients with no signs of eosinophilic inflammation accounted for 49% of participants.
The remaining 32% of patients had either isolated local/sputum eosinophilia (25%) or isolated systemic/blood eosinophilia (7%).
The researchers note in the European Respiratory Journal that “[t]hese proportions are found irrespective of asthma treatment received including high doses of inhaled corticosteroids.”
They add: “We believe our new classification based on eosinophilic inflammation is pertinent to the clinician and goes in line with the need to phenotype severe asthmatics as advocated by the recent ERS/ATS [European Respiratory Society/American Thoracic Society] guidelines.”
The presence of concomitant local and systemic eosinophilic inflammation was “strikingly” more frequent in men than women (n=53 versus 44).
And affected patients, compared with those with no eosinophilic inflammation, had a significantly lower percentage of predicted forced expiratory volume in 1 second (FEV1; 75 vs 87%), ratio of FEV1 to forced vital capacity (71 vs 75%) and provocative concentration of methacholine causing a 20% fall in FEV1 (1.49 vs 3.99 mg/mL, indicating increased bronchial hyperresponsiveness) and significantly higher fractional exhaled nitric oxide (77 vs 17 ppb).
They also had a significantly higher baseline exacerbation rate (1.5 vs 0.42 per year) and 74% of affected patients had an Asthma Control Questionnaire (ACQ) score above 1.5, while only 10% had well-controlled asthma, with an ACQ score below 0.75.
The researchers conclude that “assessment of inflammation in both airways and peripheral blood provides additional information about asthma status”, adding: “We believe our classification may be valid to start intervention studies using drugs mainly targeting either the airways or the blood compartment according to the patient’s profile.”
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