Simultaneously increased fraction of exhaled nitric oxide levels and blood eosinophil counts relate to increased asthma morbidity

• BACKGROUND: We have previously described that fraction of exhaled nitric oxide (Feno) levels and blood eosinophil counts offer additive information in relation to asthma and asthma exacerbations when analyzing data from a large population study.OBJECTIVE: We sought to investigate increased Feno levels and blood eosinophil counts in relation to lung function, bronchial hyperresponsiveness (BHR), and asthma control in a cohort of young asthmatic patients.METHODS: Measurements of Feno levels and blood eosinophil counts were available in 406 subjects (208 women) aged 10 to 35 years. Asthma control was assessed through the Asthma Control Test. Moderate-to-severe BHR was defined as a cumulative dose of methacholine of less than 0.3 mg causing an FEV1 decrease of 20%.RESULTS: Subjects with simultaneously increased Feno levels (≥20-25 ppb) and blood eosinophil counts (≥0.3 × 10(9)/L) had a higher prevalence of uncontrolled asthma (Asthma Control Test score, <20) than subjects with singly increased blood eosinophil counts (40.5% vs 21.1%, P = .01). This difference remained significant (P = .006), and a significant difference was also found between subjects with both increased Feno levels and blood eosinophil counts and subjects with normal Feno levels and blood eosinophil counts (P = .02) after adjusting for confounders. Having increased Feno levels and blood eosinophil counts related to a higher prevalence of moderate-to-severe BHR than having normal Feno levels and blood eosinophil counts or singly increased Feno levels or blood eosinophil counts (85.7% vs 35.8% or 63.3% or 60%, P < .05 all comparisons).CONCLUSION: We have shown that simultaneously increased local (Feno) and systemic (blood eosinophil) markers of type 2 inflammation related to a higher likelihood of BHR and uncontrolled asthma in a large cohort of young asthmatic patients.

Nyckelord

Habitual snoring

Epidemiology

Daytime sleepiness

Air pollution

Traffic noise

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