ILO/VCD and airway disease

Asthma, is a common and heterogeneous disease, often associated with multiple comorbidities.  It causes symptoms of cough, wheeze, shortness of breath, and chest tightness (Louis et al., 2022). When a patient experiences dyspnea or other symptoms during exercise, they are frequently diagnosed with asthma, often based solely on subjective symptoms, without a specialist respiratory consultation or objective lung function testing to support the diagnosis.

A diagnosis of asthma should not be based on symptoms alone but also on the presence of variable airflow obstruction on lung function testing.

In the recent years there has been growing evidence suggesting that ILO/VCD, despite being less known, is also a relatively common condition that can induce respiratory symptoms mimicking those of asthma (Halvorsen et al., 2017).  ILO/VCD and asthma may co-exist in up to 30% in mild to moderate asthma and 50% in severe asthma (Lewthwaite et al., 2024), further complicating the diagnostic assessment.  

The similarities and differences between ILO/VCD and asthma, as well as diagnostic evaluation and treatment are outlined below.

Asthma and ILO/VCD can have similar symptoms, but there are a few indicators that can help differentiate between the two conditions: 

ILO/VCD is a prevalent comorbidity in asthma, according to recent research.

• The incidence of ILO/VCD appears to be high in patients with asthma, ranging from 13.5% to 50%.
• Comorbid ILO/VCD in Individuals with asthma may complicate asthma management and make it more difficult to obtain asthma control due to the persistence of respiratory symptoms.
• Recognizing ILO/VCD as a comorbidity and performing a laryngeal assessment is important in the management of people with asthma, particularly when treatment with standard asthma medications fails, and patients present with symptoms that may be of laryngeal origin.

Information on the differential diagnosis between ILO/VCD and asthma can be found here

There are several ways to identify ILO/VCD in asthma (Leong et al., 2023). Briefly, ILO/VCD in asthma can be diagnosed using a laryngoscopy or a dynamic CT-scan of the larynx. These methods will be covered in greater detail in later sessions.

Continuous laryngoscopy during exercise testing (CLE-test) (Roksund et al., 2017). In this test, a laryngoscope is attached to a helmet, and the patient is asked to exercise on a stationary bike or treadmill. A real-time view of the laryngeal structures are visualised while exercising on a treadmill or a bicycle. (link)

Dynamic CT-scans of the larynx can also be used to diagnose vocal closure (link). These scans have the potential to provide a rapid disagnosis of ILO/VCD in asthma, with reasonable sensitivity (70%) and high specificity (90%) in patients with clinical suspicion of VCD/ILO following respiratory review. Currently this procedure is not widely used, however CT of the larynx can be performed wherever a cardiac CT is done, with only low radiation exposure (<1 milliSievert), and warrants further investigation.

Since symptoms of ILO/VCD and asthma may overlap, treating both the asthma and comorbid ILO/VCD is needed to improve symptom control and avoid unnecessary escalation of asthma medication.    

Patients with COPD appear to have a high rate of inspirtory vocal cord closure, but research is still at an early stage and much remains to be explored (Leong et al., 2020). ILO/VCD can coexist and share symptoms, which may lead to misdiagnosis and confusion.