Could That Chronic Cough Be Asthma?

Persistent, dry cough of more than 8 weeks may be a clue

Cough Variant Asthma (CAV)
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A chronic cough is considered a classic symptom of asthma, typically in association with wheezing, chest tightness, and shortness of breath. Together, they form the profile of symptoms that help doctors make an asthma diagnosis.

But there are times when a cough is the only symptom present. And, while it can certainly be attributed to any number of things, there may be features which suggest that it's a less-common condition known as cough variant asthma (CVA).

Characteristics of Cough Variant Asthma

CVA is a form of asthma whose primary characteristic is a chronic, non-productive (dry) cough. It is considered by some to be a precursor to "classic" asthma wherein the cough may be the first sign of several symptoms yet to come. Studies have suggested that it may be more common than believed and that anywhere from a quarter to a third of patients with a chronic cough may, in fact, have CVA.

Generally speaking, people with CVA have several key features that distinguish them from people with classic asthma. People with CVA have a far more sensitive cough reflex than those with classic asthma.

And, while both CVA and classic asthma are characterized by hyperresponsiveness (increased airway sensitivity), people with CVA often have less, if any, reaction to methacholine, an inhaled compound used to diagnose asthma in borderline patients.

Ultimately, the defining features of CVA is a dry cough that lasts for eight weeks or more, occurs either night or day, and produces little, if any, mucus.

How Cough Variant Asthma Is Diagnosed

Diagnosing CVA is considered important as the very persistence of a cough decreases a person's quality of life. The main challenge, therefore, is identifying the condition when there is no other evidence of asthma. While a spirometry test (which measures respiratory function) may be performed, people with CVA will often have no measurable evidence of lung obstruction.

In such case, methacholine may be used to trigger hyperresponsiveness as part of a bronchial provocation test. If it is unable to do this, other triggers such as cold, exercise, or histamines may be used. If none of these things are able to elicit a response, then CVA is unlikely.

But, even if there is a reaction, hyperresponsiveness alone does not make a diagnosis. Within the context of CVA, a definitive diagnosis can only be made if the hyperresponsiveness is relieved using an asthma medication called a bronchodilator.

Alternately, the doctor may look at your sputum under the microscope for evidence of a white blood cell called an eosinophil. An increased eosinophil count often occurs in response to an allergy. Similar, a breath test for exhaled nitric oxide (an inflammatory gas released from lung cells) is highly predictive of CVA even if all other tests are inconclusive.

Treating Chronic Variant Asthma

Treatment of CVA is virtually the same as for classic asthma. The use of a bronchodilator like albuterol may provide partial relief in as quickly as a week. More severe coughs may be treated with an inhaled steroid like Flovent. If inhaled treatment is unable to fully resolve the cough, oral steroids like prednisone may be used.

Additionally, if there is evidence of eosinophilia, an anti-inflammatory drug like Zafirlukast has been shown to improve cough in people for whom inhaled steroids have failed.

Sources;

Niimi, A. "Cough and Asthma." Curr Respir Med Rev. 2011; 7(1): 47-54.

Matsumoto, H.; Niimi, A.; Takemura, M.; et al. "Prognosis of cough variant asthma: a retrospective analysis." J Asthma. 2006; 43(2):131-135.

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