Association of Exhaled Nitric Oxide to Asthma Burden in Asthmatics on Inhaled Corticosteroids

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 (NIOXMINO (R)) 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.