Breathing Out the Truth: What Fractional Exhaled Nitric Oxide Really Tells Us About Pediatric Asthma

Asthma is the most prevalent chronic respiratory disease in childhood, and the objective assessment of airway inflammation remains a major challenge, particularly in younger children in whom conventional lung function testing is often not feasible. The aim of this narrative review is to evaluate the clinical role of fractional exhaled nitric oxide (FeNO) in pediatric asthma, focusing on its diagnostic utility, role in treatment guidance, and value in disease monitoring. A structured literature search was conducted in PubMed for studies published between January 2015 and October 2025, using predefined keywords related to FeNO, asthma, and pediatric populations. After applying the eligibility criteria, 47 studies were included in the final synthesis. Evidence from systematic reviews and clinical studies indicates that FeNO has moderate-to-good diagnostic accuracy for childhood asthma, with a pooled sensitivity of 0.79 and specificity of 0.81, and is most useful as an adjunct to clinical assessment and lung function testing. FeNO-guided therapy may reduce exacerbation rates in selected pediatric populations, although its effects on symptom control and corticosteroid use remain inconsistent. In the monitoring setting, serial FeNO measurements may provide additional information on inflammatory control, treatment adherence, and risk of future exacerbations. However, interpretation is influenced by multiple confounding factors, including atopy, allergic rhinitis, corticosteroid therapy, and asthma phenotype. In conclusion, FeNO is a valuable complementary biomarker in pediatric asthma, with particular utility in improving diagnostic and therapeutic precision. Its optimal use requires careful integration within a multimodal clinical framework rather than reliance as a standalone tool.