Predictive value of fractional nitric oxide in asthma diagnosis-subgroup analyses

Abstract

Background: There are no studies investigating the benefit of using FeNO measurements in correlation with sensitization to perennial and seasonal allergens in children with asthma.

Objective: To define the group of children with respiratory symptoms in whose FeNO measurement has predictive value for asthma. We assessed the effect of age, allergy profile, atopy, lung function and the presence of allergic rhinitis on interpretation of FeNO levels for clinical applications.

Methods: It was a retrospective, cross-sectional study. We evaluated data from medical documentation of 1767 children with symptoms of allergic diseases such as asthma and/or allergic rhinitis. We included in the analyses subjects who had the following tests done during diagnostic procedures (single measurement): FeNO, spirometry, specific IgE results. All subjects had undergone a minimum 3-years prospective clinical observation after the first FeNO measurement until the later assignment (or not) of an asthma/allergic rhinitis diagnosis.

Results: We included 1767 children into the analysis; asthma diagnosis was confirm in 1054 (59.6%) children. We showed that only atopy (OR: 1.9; 95%CI: 1.5-2.4) and presence of allergic rhinitis (OR: 1.6; 95%CI: 1.4-1.9) were independently associated with increased FeNO level. Only among patients with atopy and allergic rhinitis FeNO level (above 23 ppb) was associated with asthma diagnosis. Sensitivity, specificity, positive predictive value and negative predictive value of FeNO >23 ppb for asthma diagnosis were as follows: 0.9(95%CI: 0.68-0.98), 0.52(95%CI: 0.42-0.61), 0.25(95%CI: 0.16-0.37), 0.97(95%CI: 0.88-0.99).

Conclusion: We showed that in children with atopy and with allergic rhinitis a negative predictive value for asthma diagnosis was very high with the optimal cut-off point of FeNO 23 ppb. Therefore we showed the utility of FeNO measurements to exclude asthma in the subgroup of patients with atopy and allergic rhinitis.

Keywords: Asthma; FeNO; Schoolchildren.