Background: Fractional exhaled nitric oxide (FENO) is a marker of airway inflammation. Its role in assessing asthma burden in clinical practice needs more study.
Objective: To determine whether higher FENO levels are associated with greater asthma burden.
Methods: This was a multicenter cross-sectional retrospective study of atopic 12- to 56-year-old persistent asthmatics on inhaled corticosteroids (ICS). Questionnaire and 1-year retrospective administrative data were used to analyze by unadjusted and adjusted robust Poisson regression (relative risks) and negative binomial regression [incidence rate ratios (IRRs)] the associations of masked FENO levels (NIOX MINO®) to short-acting beta-agonist (SABA) dispensings and oral corticosteroid (OCS) use in the past year independent of spirometry and an asthma control tool [Asthma Control Test (ACT)].
Results: FENO levels ranged from 7-215 ppb (median 28 ppb) in 325 patients. Higher FENO levels significantly correlated with more SABA dispensings and OCS courses in the past year, lower FEV(1)% predicted levels, but not ACT score. FENO highest (≥48 ppb) versus lowest (≤19 ppb) quartile values were associated independently in the past year with ≥7 SABA canisters dispensed (relative risk=2.40, 95% CI=1.25-4.62) and total number of SABA canisters dispensed (IRR=1.46, 95% CI=1.12-1.99) and with ≥1 OCS course (relative risk=1.48, 95% CI=1.06-2.07) and total number of OCS courses (IRR=1.71, 95% CI=1.09-2.66). The significant independent relationship of higher FENO levels to increasing SABA dispensings and OCS courses was confirmed by linear trend analyses.
Conclusions: Independent and clinically meaningful associations between higher FENO levels and greater asthma burden during a prior year in persistent asthmatics on ICS suggest that FENO measurement may be a complementary tool to help clinicians assess asthma burden.