Diagnostic Value of Lung Function Parameters and FeNO for Asthma in Schoolchildren in Large, Real-Life Population

Background and Objective: To establish a diagnostic value of fractional exhaled nitric oxide (FeNO), interrupter resistance measurement (Rint), specific resistance of the airways (sRaw), spirometric parameters in asthma diagnosis in schoolchildren. Methods: It was a retrospective, cross-sectional study. We evaluated data from medical documentation of 6,439 children (aged 6-18) with symptoms suggestive of asthma, who attended our Pediatric Allergic Outpatient Clinic. Medical documentation of the patients was analyzed with special attention to the first ever obtained results (before the introduction of controller medication) of: FeNO, Rint, sRaw, spirometry, diagnoses of allergic diseases, and allergen sensitization (specific IgE results). Results: We included 3,612 children in the analysis. Older age, male gender, the presence of allergic rhinitis, sensitization to perennial and seasonal allergens, higher FeNO and Rint, and FEV1/FVC <80% were significantly associated with asthma. We observed a significant association between FeNO and Rint in the prediction of asthma diagnosis. Optimal cutoff points to differentiate asthmatics from non-asthmatics were established. Thus, Rint > 175.4% was defined as asthma-predicting Rint, and FeNO > 15.8 ppb was defined as asthma-predicting FeNO. In all study subgroups, sensitivity for asthma-predicting Rint was significantly higher than for asthma-predicting FeNO with an inverse trend in specificity value. Conclusion: Our results suggest that asthma-predicting Rint and, to a lesser extent, asthma-predicting FeNO, defined in the present study, could serve as a reliable tool to exclude asthma in schoolchildren. However, our results also indicate a clinically important fact that all lung function parameters or FeNO should be interpreted in the context of age, gender, allergy profile, and the presence of co-morbidities in schoolchildren. (C) 2013 Wiley Periodicals, Inc.