Fração exalada de óxido nítrico em adolescentes com rinite e asma detectadas pelo questionário ISAAC

Abstract

BACKGROUND: Asthma is one of the most common chronic diseases and, according to the International Study on Asthma and Allergies in Childhood - ISAAC -, affects up to 30% of Brazilian adolescents. Allergic rhinitis (AR) is a symptomatic disorder of the nasal airways, often associated with asthma. Both have important inflammatory component, are induced by allergen exposure and detection of atopy is relevant for preventive and therapeutic measures. Multiple cells and mediators participate in the airways inflammation, including nitric oxide. Monitoring the degree of inflammation is indicated for asthma control, being considered clinical parameters and markers as fractional exhaled nitric oxide measurement - FeNO. OBJECTIVE: To assess FeNO in adolescents with asthma and AR detected by the ISAAC questionnaire, as well as the association of this marker with atopy, asthma control, quality of life and obesity. METHODS: Observational cross-sectional study. After answering ISAAC questionnaire, the adolescents were evaluated for: anthropometric measures (weight, height, triceps (TF) and subscapularis (SF) folds), spirometry, FeNO, atopy by skin prick test and quality of life (QOL). For data analysis, we used the SPSS version 15.0. Normality was verified by the Shapiro-Wilk test and the Student t test, Mann-Whitney U and ANOVA with post-hoc Bonferroni were used for means of comparison. The chi-square test with Cramér index was used to compare categorical variables and was considered a significance level when p ≤ 0.05. RESULTS: 161 questionnaires were applied, 66 adolescents were detected with asthma and 83 with AR. 55 teenagers aged 14,5 ± 0,93 years were allowed to participate: 37 had asthma and/or AR and 18 did not. In the asthma group (29), FeNO was high (median: 49 ppb) and was inversely associated with the disease control (r = 0.417; p = 0.03) and QoL (r = -0.578; p = 0.002); FeNO, when higher than 25 ppb, was associated with obesity by BMI (Cramér level: 0.68, p: 0.004), TF (Cramér level: 0.47, p: 0.04) and SF (Cramér Index: 0.56; p: 0.02) only in the group without asthma or RA. From 31 adolescents with asthma and/or AR, 23 had positive skin prick test and FeNO was significantly higher (p <0.001). CONCLUSION: The degree of inflammation of the lower airways assessed by FeNO is elevated in asthma and RA, confirms the diagnosis through ISAAC questionnaire and is not associated with obesity; in asthmatic adolescents, it can predict uncontroled disease and impaired QoL. In adolescents without asthma, FeNO seems to reflect the presence of obesity.