Validation of the Dyspnea Index in Adolescents With Exercise-Induced Paradoxical Vocal Fold Motion

IMPORTANCE: Paradoxical vocal fold motion (PVFM) affects almost 1 million adolescents in the United States. However, to date, no disease-specific objective measure exists to assess symptom severity and response to treatment in adolescents with exercise-induced PVFM. OBJECTIVES: To validate the Dyspnea Index (DI) quality-of-life instrument (previously validated for adults with breathing disorders) in children aged 12 to 18 years with exercise-induced PVFM and to determine the minimum significant DI change corresponding to patient-reported or caregiver-reported improvement or worsening of symptoms. DESIGN, SETTING, AND PARTICIPANTS: A longitudinal study of 56 patients (age range, 12-18 years) diagnosed as having exercise-induced PVFM and their caregivers from February 1, 2013, to September 30, 2013, in an outpatient pediatric otolaryngology office practice. INTERVENTIONS: The DI was administered to patients and caregivers, with items modified to reflect the perspective of caregivers. MAIN OUTCOMES AND MEASURES: Appropriate DI change was measured to reflect improvement or worsening of symptoms. Test-retest reliability was accomplished by having a subset of patients and caregivers complete the instrument twice within 2 weeks before therapy. Internal consistency was assessed by calculation of Cronbach α. Discriminant validity and convergent validity were determined by comparing DIs with assessment of global change in symptoms. RESULTS: The patient and caregiver mean (SD) DI changes were -12.9 (9.6) and -14.7 (9.3), respectively (P < .001 for both). Reliability was established by test-retest analysis with an intraclass correlation coefficient of 0.8 and by calculation of Cronbach α = 0.80, demonstrating internal consistency. Discriminant validity was determined by assessing for a significant DI change when patients globally perceived that a change existed after treatment (P < .001). A DI change of 8 or higher (P < .001) correlated with patient-reported significant change. Convergent validity was demonstrated by evaluating for significant DI change when no change was reported following treatment (P < .001). CONCLUSIONS AND RELEVANCE: The DI appears to be a valid and reliable instrument to assess quality of life in exercise-induced pediatric PVFM. A DI change of 8 or higher seems significant. This instrument can serve as an objective tool to assess change in exercise-induced pediatric PVFM following speech therapy.