AbstractRationale for the studyVocal cord dysfunction (VCD) often presents with dramatic and abrupt symptoms. To diagnose VCD, visualization by direct laryngoscopy is required and because patients are usually asymptomatic, a specific method to provoke VCD is needed. Approaches to predict VCD by alterations of the flow‐volume loop have been investigated.MethodsAdolescents with clinical suspicion of VCD were invited to participate. After an initial pulmonary function test (PFT), direct laryngoscopy was performed. This was followed by a methacholine challenge test (MCT); the methacholine dose causing a 20% drop in forced expiratory volume after 1 sec (FEV1) (PD20FEV1) was calculated. Then a second laryngoscopy was conducted. PFT changes before and after MCT were compared with the data of 14 healthy controls (HCs).ResultsThirty‐five patients (8–19 years) were investigated. Three showed anatomical alterations. Of the remaining 32 patients, 14 had VCD and 18 had bronchial hyperresponsiveness (non‐VCD). In 29 patients with a positive MCT, PD20FEV1 methacholine was significantly lower in VCD compared with non‐VCD (VCD 0.24 ± 0.4 mg, non‐VCD 0.73 ± 0.73 mg, P = 0.0006). A PD20FEV1 < 0.24 mg methacholine predicted VCD with a sensitivity of 85% and a specificity of 75%. VCD patients showed significantly lower PFT parameters after challenge; FEV1: VCD 58.5 ± 20.1%, non‐VCD 80.2 ± 18.0%, and HCs 98.7 ± 16.6% (P < 0.0001).ConclusionsThe combination of MCT and laryngoscopy may be able to differentiate between VCD and non‐VCD. VCD patients showed a positive reaction at lower methacholine doses and displayed greater airway obstruction after MCT. PFTs and MCT do not replace direct laryngoscopy in the diagnosis of VCD in adolescents. Pediatr Pulmonol. 2012; 47:612–619. © 2012 Wiley Periodicals, Inc.