Development and validation of the Exercise-Induced Laryngeal Obstruction Dyspnea Index (EILODI).

Background: Exercise-induced laryngeal obstruction (EILO) causes exertional dyspnea and is important for its effect on quality of life, diagnostic confusion with exercise-induced asthma, and health care resource utilization. There is no validated patient-reported outcome measure specific to EILO.

Objective: We sought to develop, validate, and define a minimal clinically important difference for a patient-reported outcome measure to be used with adolescents and young adults with EILO.

Methods: A multidisciplinary group created a preliminary measure, modified by a 10-member participant focus group, with 20 items scored along a 5-point Likert scale. A subsequent cohort of participants recruited from a clinic, aged 12 to 21 years, with confirmed EILO by continuous laryngoscopy during exercise testing (1) completed the measure at 3 points in time over 28 days and (2) provided anchoring data in the form of a daily exercise log and categorical self-assessments of clinical improvement. Thirty additional participants without exertional dyspnea served as controls.

Results: Two hundred nineteen subjects with mild to severe EILO participated in the exploratory factor analysis, which identified 7 factors within the preliminary outcome measure. After a process of item reduction, a 12-item metric with a total score ranging from 0 to 48 was developed. Mean scores of patients with EILO and healthy controls at baseline were 28.8 ± 7.4 and 4.5 ± 7.4, respectively. A minimal clinically important difference of 6 was determined by comparison of index change with changes in categorical self-assessments of improvement.

Conclusions: This is the first patient-reported outcome measure specifically designed for adolescents and young adults with EILO.