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 (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.

Asthma population management: development and validation of a practical 3-level risk stratification scheme.

OBJECTIVE: To define and validate a practical risk stratification scheme based on administrative data for use in identifying patients at high, medium, and low risk of requiring emergency hospital care for asthma. STUDY DESIGN: Retrospective cohort. PATIENTS AND METHODS: Predictors in 1999 were evaluated in relation to 2000 asthma emergency hospital care (any asthma hospitalization or emergency department visit) in a training set (n = 8789, 2000 emergency hospital care = 5.5%) and a testing set (n = 6104, 2000 emergency hospital care = 7.9%). Logistic regression was used to assign risk points in the training set, and positive and negative predictive values, sensitivities, and specificities were calculated in the training and testing sets. RESULTS: High risk was defined as asthma emergency hospital care in the previous year or use of >14 beta-agonist canisters and oral corticosteroid use; medium risk was defined as no emergency hospital care but use of either >14 beta-agonist canisters or oral corticosteroids; and low risk was defined as none of the above. For the high-risk groups in the training and testing sets, positive predictive values were 12.9% and 22.0%, sensitivities were 24.8% and 25.4%, specificities were 90.3% and 92.0%, and negative predictive values were 95.4% and 93.2%, respectively. The medium-risk groups identified another 32.6% of patients in the training set and 28.3% in the testing set requiring subsequent asthma emergency hospital care. CONCLUSION: This simple risk stratification scheme is useful for identifying patients from administrative data who are at increased risk of experiencing emergency hospital care for asthma.