Which test is most appropriate to confirm the diagnosis of laryngomalacia?

Direct laryngoscopy is the most appropriate test to confirm the diagnosis of laryngomalacia because it allows for direct visualization of the larynx and surrounding structures. In laryngomalacia, the soft and floppy tissue above the vocal cords collapses inward during breathing, leading to the characteristic stridor often observed in infants. Direct laryngoscopy enables the clinician to observe these structural abnormalities firsthand and to assess the severity of the condition accurately, thus confirming the diagnosis.

Other imaging techniques, such as X-ray of the neck or flexible bronchoscopy, do not provide the same level of detail regarding the laryngeal anatomy and dynamics during breathing. A barium swallow study is focused on evaluating swallowing function and does not provide information relevant to laryngomalacia. Therefore, direct laryngoscopy is the gold standard for diagnosis in this case.