Precision of bronchoprovocation testing in the diagnosis of exercise-induced laryngeal obstruction

Abstract

Introduction: Exercise-induced laryngeal obstruction (EILO) is a key differential diagnosis for asthma in the presence of excertional respiratory symptoms. Continuous laryngoscopy during exercise (CLE), the current gold standard diagnostic test for EILO, has practical limitations. We aimed to establish if inspiratory flow data obtained during standard bronchial provocation testing (BPT) may prove diagnostic for EILO and thus preclude a requirement for CLE testing. Methods: We consecutively evaluated 37 adult subjects with possible asthma referred over a 6-month period to an outpatient clinic. All subjects received comprehensive assessment including a detailed clinical evaluation, pulmonary function testing, indirect and direct BPTs and a CLE test. All continuous variables with P ≤0.20 in univariate testing were included in a multiple regression analysis with backward elimination. Results: Moderate or severe EILO was diagnosed in 8 subjects (22%). In a multiple linear regression analysis, neither the relative nor the absolute decrease in FIF 50 in Mannitol and Methacholine BPTs were able to predict EILO sum score. The final model containing sex and height was statistically significant, F (2,34)=8.697; P =0.001 and accounted for 30% of the variance of EILO sum score ( R 2 =0.338; adjusted R 2 =0.300). Female sex (B=0.756; P P =0.038) were significant predictors of EILO sum score. Conclusion: Inspiratory flow parameters in BPTs combined with a thorough evaluation of symptoms provides valuable information in the clinical investigation of this patient group, yet is insufficiently precise to preclude the need for CLE.