Simultaneously elevated exhaled nitric oxide and serum‐eosinophil cationic protein relate to recent asthma events in asthmatics in a cross‐sectional population‐based study

SummaryBackgroundWe have reported that increased fraction of exhaled nitric oxide (FeNO), a measure of TH2‐driven airway inflammation, and blood eosinophil count, a marker of systemic eosinophil inflammation, correlated with asthma attacks in a population‐based study.ObjectiveTo investigate the relation between simultaneously elevated FeNO and serum eosinophil cationic protein (S‐ECP) levels and asthma events among asthmatics.MethodsMeasurements of FeNO (elevated ≥ 25 ppb) and S‐ECP (elevated ≥ 20 ng/mL) were performed in 339 adult asthmatics. Asthma events (attacks and symptoms) were self‐reported.ResultsSimultaneously normal S‐ECP and FeNO levels were found in 48% of the subjects. Subjects with simultaneously elevated S‐ECP and FeNO (13% of the population) had a higher prevalence of asthma attacks in the preceding 3 months than subjects with normal S‐ECP and FeNO (51% vs. 25%, P = 0.001). This was not found for subjects with singly elevated S‐ECP (P = 0.14) or FeNO (P = 0.34) levels. Elevated S‐ECP and FeNO levels were independently associated with asthma attacks in the preceding 3 months after adjusting for potential confounders (OR (95% CI) 4.2 (2.0–8.8).ConclusionsSimultaneously elevated FeNO and S‐ECP levels were related to a higher likelihood of asthma attacks in the preceding 3 months. This indicates that there is a value in measuring both FeNO and systemic eosinophilic inflammation in patients with asthma to identify individuals at high risk of exacerbations.Clinical relevanceFeNO and S‐ECP are markers for inflammation in asthma, but are dependent on different inflammatory pathways and weakly correlated. Simultaneous measurements of both offer better risk characterization of adult asthmatics.