Abstract
Inducible laryngeal obstruction (ILO) is often misdiagnosed as, or may coexist with, asthma. Identifying differences in triggering factors may assist clinicians to differentiate between the two conditions and could give mechanistic insights. To identify and compare patient-reported triggers in ILO and asthma. This was a two-part study. Initially, we conducted a retrospective case note review of the triggers of ILO from endoscopically confirmed ILO patients to generate a Breathlessness Triggers Survey (BrTS). Triggers were categorized as scents, environmental factors, temperature, emotions, mechanical factors and daily activities. Secondly, ILO and/or asthma patients completed the BrTS prospectively, rating the likelihood of each item triggering their symptoms using a five-point Likert scale (strongly disagree to strongly agree). Chi-square testing was performed to compare responses by cohort. Data from 202 patients with ILO [73% female, mean (SD) age 53(16) years] were included in the case note review. For the prospective study, 38 patients with ILO only [63% females, age 57(16) years], 39 patients with asthma only [(56% female, age 53(13) years] and 12 patients with both ILO and asthma [83% female, mean age, 57 (14) years)] completed the BrTS. The triggers identified in the case note review were confirmed in the independent sample of patients with ILO and/or asthma and identified several difference in prevalence of the triggers between disease types. Mechanical factors (talking [P<.001], shouting [P=.007] and swallowing [P=.002]) were more common in the ILO cohort compared to patients with asthma. Environmental factors (pollen/flowers [P=.005] and damp air [P=.012]) were more common in asthma. There were no differences between groups in frequency of reporting scents as triggers (except for vinegar, more common in ILO, P=.019), temperature, emotions or daily activities. There were notable differences between patient-reported triggers of ILO and asthma, which may support clinician differential diagnosis.
Highlights
Inducible laryngeal obstruction (ILO) is often misdiagnosed as, or may coexist with, asthma
Environmental factors Smoke/fumes affected more than 80% of both cohorts without a between-group difference in frequency (P > .05), whereas damp and pollen/flowers were more problematic for the asthma group compared to those with ILO (71% versus 46%, P = .012 and 78% versus 52%, P = .005, respectively) (Figure 1B)
Mechanical factors There was a significant difference between the ILO and asthma cohorts for three of the four mechanical triggers; talking (78% versus 41%, P < .001), shouting (80% versus 55%, P = .007) and swallowing (66% versus 35%, P = .002), but not laughing (68% versus 59%, respectively, P = .339) (Figure 1C)
Summary
Inducible laryngeal obstruction (ILO) is an umbrella term for a group of conditions associated with acute breathlessness caused by episodic airflow obstructions arising in the larynx, most commonly manifesting as paradoxical adduction of glottic and/or supraglottic folds during inspiration, often referred to as vocal cord dysfunction.[1]. A recent systematic review highlighted ILO as a comorbidity in quarter of asthma cases where ILO was identified by visualization of laryngeal movement, with the value increasing to over one third when the ILO diagnosis included a provocation stimulus.[5] Further, in two prospective studies, of difficult-to-treat asthma and where ILO was suspected in asthmatic patients, up to 50% of patients were identified as suffering concomitant ILO and asthma.[6,7] Both asthma and ILO may present with dyspnoea and wheezing upon exposure to certain triggers such as physical exertion or inhaled irritants, making differentiation between the two conditions a clinical challenge.[7] Due to the similarities in presentation, many people with underlying ILO are misdiagnosed with refractory asthma. The identification of disease-specific triggers may lead to novel hypotheses related to upper and lower airway hyperresponsiveness
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