This study looked at how well a breath test called fractional exhaled nitric oxide (FeNO) can diagnose asthma in school-age children who were referred for suspected asthma. The research involved 1,979 children in a Swiss cohort, and the reference for a true asthma diagnosis was made by pediatric pulmonologists.
The main finding was that FeNO had poor overall accuracy for diagnosing asthma, with a statistical measure of discrimination showing it was only slightly better than chance. The test was better at ruling out asthma (high specificity) than at confirming it (low sensitivity). Its ability to correctly identify children with asthma was especially low in those without allergic sensitization, where it showed no diagnostic value.
The study did not report any safety concerns, as it was a diagnostic accuracy study. The main reason to be careful is that the test's performance varies greatly depending on a child's allergy status and the local prevalence of asthma. This means the results may not apply to all groups of children.
From this single observational study, readers should understand that FeNO is not a reliable standalone test for diagnosing asthma in school-age children. Its usefulness may be limited, and interpretation should consider a child's specific allergic characteristics.