Fractional Exhaled Nitric Oxide Cut-off Values for Discriminating Asthma Exacerbation and Control in Indian Children with Coexisting Allergic Rhinitis: A Prospective Observational Cohort Study
摘要
To determine Fraction of exhaled nitric oxide (FeNO) cut-off values that discriminate asthma exacerbation from control in Indian children with asthma and coexisting allergic rhinitis. Also, to evaluate the correlation between FeNO and Absolute eosinophil count (AEC).
MethodsA prospective observational cohort study with repeated measurements was conducted at a tertiary-care hospital in western India (March 2023–December 2024). Children aged 4–12 y with both conditions were consecutively enrolled. FeNO and AEC were measured at baseline, 1 mo and 3 mo. Asthma and allergic rhinitis case definition followed Global Initiative for Asthma (GINA) 2023 and Allergic Rhinitis and its Impact on Asthma (ARIA) 2016 guidelines. Optimal cut-offs were derived by ROC analysis with the Youden index.
ResultsNinety-seven children (mean age 7.3 ± 2.2 y; 62.4% males) completed follow-up. FeNO and AEC correlated significantly during exacerbation (r = 0.361, p = 0.003) and control (r = 0.292, p = 0.036). A FeNO >20.5 ppb discriminated exacerbation with 77% sensitivity, 81% specificity, NPV 92.6%, PPV 52.6% (AUC 0.867, 95% CI 0.815–0.920; p <0.0001); the corresponding AEC was 505 cells/µL (AUC 0.828, 95% CI 0.769–0.887). For control, FeNO <14.5 ppb showed 55% sensitivity, 87% specificity, NPV 71% (AUC 0.739, 95% CI 0.675–0.803); corresponding AEC was 413 cells/µL.
ConclusionsFeNO and AEC are useful, complementary biomarkers in Indian children with asthma and coexisting allergic rhinitis. The proposed thresholds (FeNO >20.5 ppb for exacerbation, <14.5 ppb for control) are substantially lower than American Thoracic Society (ATS)/ European Respiratory Society (ERS) recommendations, supporting population-specific paediatric reference values.