Clinical and Inflammatory Correlates of Fractional Exhaled Nitric Oxide in Turkish Children and Adolescents with Asthma: Exploratory Analysis of the FCER2 rs2228137 Polymorphism

Background/Objectives: Fractional exhaled nitric oxide (FeNO) is a noninvasive biomarker of eosinophilic airway inflammation in asthma, but data on its clinical correlates in Turkish children and adolescents are limited. This study aimed to determine which clinical and inflammatory characteristics were independently associated with FeNO and, as a secondary exploratory objective, to assess whether the FCER2 rs2228137 (R62W) polymorphism is associated with FeNO and related clinical features.