Vocal Cord Dysfunction Workup

Updated: Mar 30, 2016
  • Author: Praveen Buddiga, MD; Chief Editor: Michael A Kaliner, MD  more...
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Workup

Laboratory Studies

Laboratory studies may be indicated to exclude other diagnoses.

Eosinophil count

Eosinophilia may suggest the diagnosis of asthma if levels are greater than 5%, but absence of this sign does not clearly exclude the diagnosis, especially if the patient has been frequently treated with oral corticosteroids.

Elevated eosinophil counts may also be observed in skin diseases such as atopic dermatitis and in clinical entities such as pulmonary infiltrates with eosinophilia, allergic bronchopulmonary aspergillosis (ABPA), Churg-Strauss syndrome, and parasitic diseases.

Vocal cord dysfunction (VCD), itself, is not associated with an elevated blood eosinophil count.

Serum immunoglobulin E (IgE) assay

Elevated serum IgE is observed in allergic individuals, but it is not specific for asthma.

This elevation may be observed in other syndromes such as ABPA and Churg-Strauss syndrome. Its presence may indicate a concomitant diagnosis of asthma even though its absence is not exclusionary.

VCD by itself is not associated with an elevated serum IgE level.

Arterial blood gases (ABG)

ABG findings reveal an alveolar-arterial gradient (ie, the alveolar-arterial oxygen difference), which is a measure of oxygen delivery from the lungs to blood, that is usually within reference ranges in the subset of patients with VCD.

In patients with acute asthma, ABG findings may be abnormal, indicative of hypoxemia.

C1 inhibitor and C4 levels

These levels should be evaluated to exclude hereditary angioedema.

This is especially useful if episodes have been prolonged (1-4 d) or if angioedema in other areas or unexplained abdominal pain has occurred in or out of association with episodes of dyspnea.

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Imaging Studies

Chest radiography

Radiographic findings are usually normal, or radiographs may show hyperinflation in asthmatic individuals.

Chest radiography may be used to evaluate other pulmonary diseases or structural laryngeal and cardiac abnormalities that may explain or support the patient's respiratory symptoms.

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Other Tests

Pulmonary function test

Spirometric testing supports the diagnosis of VCD in symptomatic individuals. [23] This study is used to identify individuals with asthma or other pulmonary abnormalities, including upper airway obstruction. In patients without coexisting asthma, spirometric findings are usually within the reference range during an episode. [10, 24] If flows are decreased during an episode, forced vital capacity (FVC) decreases in tandem with forced expiratory volume in the first second (FEV1), which is not consistent with classic airflow limitation.

Flow-volume loops are the most useful tool in discriminating between VCD and asthma. Flow-volume loops typically demonstrate inspiratory loop flattening, ie, an inspiratory flow decrease during symptomatic periods suggestive of VCD. In addition, during VCD symptoms, an abrupt drop and rise in the expiratory flow volume loop may be observed in the absence of coughing. See the image below.

Flow volume loops. Flow volume loops.

Results of routine measurement of airflow obstruction (ie, FEV1, peak expiratory flow rate) can be within reference ranges in VCD if the vocal cords close only on inspiration. If vocal cord closure occurs during both inspiration and expiration, FEV1 can decrease along with the decrease in FVC, making the FEV1/FVC ratio within the reference range. This distinguishes isolated VCD from VCD concomitant with asthma, in which the FEV1 is proportionately decreased more than the FVC, representing airflow limitation.

The Pittsburgh Vocal Cord Dysfunction Index

In 2014, researchers developed a scoring index to help distinguish VCD from asthma. Researchers identified symptoms of throat tightness and dysphonia, the absence of wheezing, and the presence of odors as a symptom trigger as key features of VCD that distinguish it from asthma. The index showed good sensitivity (83%) and specificity (95%), and accurately diagnosed VCD in 77.8% of patients with laryngoscopy-proven VCD. [25]

Methacholine provocation

A patient with VCD shows no bronchial hyperresponsiveness on methacholine challenge unless he or she has concomitant asthma.

This challenge is therefore most helpful in excluding the diagnosis of asthma. It may also be helpful in confirming that a patient with VCD has coexisting asthma.

Exercise provocation

In a patient in whom exercise or strenuous activity is a primary trigger, a graded exercise challenge on a bicycle ergometer or treadmill is helpful to establish a diagnosis.

Allergy skin testing

Perform skin tests to determine the existence of an allergic or environmental trigger or condition (eg, allergic rhinitis, allergic asthma).

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Procedures

Laryngoscopy

The criterion standard for the diagnosis of VCD is direct visualization of the paradoxical adduction of the true vocal cords during inspiration. [2, 26, 23]

The classic textbook picture is the adduction of the anterior two thirds of the vocal cords with a posterior diamond-shaped chink through which air flows during the inspiratory phase.

Laryngoscopic views of the vocal cords. Laryngoscopic views of the vocal cords.

If the patient is not symptomatic at the time of laryngoscopy or rhinoscopy, typical vocal cord changes may often be induced by exercise, hyperventilation, or a maximal forced expiratory effort followed by rapid inspiration. These maneuvers may increase the sensitivity of the test. [27, 28, 29]

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