This Study Aims to Compare Asthma Control in Children Monitored With FeNO Against a Historical Cohort Without FeNO. Secondary Objectives Include Evaluating Associations Between FeNO Levels, ACT/C-ACT Scores, Eosinophil Counts, FEV1%, ICS Adherence, and Exacerbation Frequency.

Registration: Eligible participants will be registered consecutively during clinic visits after obtaining informed consent (and assent where applicable). * Randomization: As this is an observational study comparing prospective data with historical controls, no randomization will be performed. 2.4 Data Gathering Methods * Prospective FeNO Group: Monthly data collection over 3 months including ACT/ C-ACT questionnaires, FeNO measurements using portable point-of-care devices, spirometry (FEV1%), and peripheral blood eosinophil counts. * Historical Control Group: Extraction of relevant clinical data (ACT/C-ACT scores, spirometry, eosinophil counts, ICS adherence, and exacerbation records) from electronic medical records covering a comparable 3-month timeframe. 2.5 Procedures and Central Laboratories * FeNO measurements will be conducted using a validated, portable FeNO device standardized across study sites. * Spirometry will be performed according to American Thoracic Society guidelines