Understanding Cough Variant Asthmaby Kathi MacNaughton Health Professional
Cough variant asthma, or CVA for short, is a less common form of asthma that is characterized by the fact that its only symptom is a chronic cough. People who have CVA do not generally have the other common symptoms of asthma, such as wheezing, shortness of breath and chest tightness. CVA is an especially common diagnosis in young children, and it often progresses into full-blown asthma down the line.
The cough in cough variant asthma is a dry cough that lasts for more than 6 to 8 weeks. It can occur any time of the day, though coughing at night that wakes you up is common with CVA. The cough also often worsens during exercise. Other conditions, such as respiratory infections, can cause a chronic cough, but when the cough lasts longer than a few weeks in the absence of an active infection, doctors will suspect CVA.
Diagnosing cough variant asthma, however, can be difficult. Unlike with regular asthma, people with CVA usually have normal pulmonary function tests, such as spirometry. So, to nail down the CVA diagnosis, another type of test called a methacholine challenge test, will be needed.
A methacholine challenge measures microscopic changes in the airways that are typical of cough variant asthma. With this test, the person inhales increasing amounts of an aerosol mist called methacholine while performing spirometry. While that is going on, the doctor watches for the airways to spasm and narrow. If lung function drops by 20% or more, then a diagnosis of asthma will be made.
Methacholine challenges must be done in a special facility, so sometimes doctors will decide just to initiate asthma treatment instead, in the absence of a diagnosis. If the person responds positively, that is the cough eases, with treatment, then the person is considered to be positive for cough variant asthma too.
The treatment for cough variant asthma is the same as for regular asthma -- an inhaled steroid for daily or twice daily control, plus a short-acting bronchodilator as a rescue inhaler when symptoms do crop up. It can take a week or two for the cough to be relieved when therapy first starts.
Also, some people with CVA find that using an inhaler actually stimulates the cough reflex. If that happens, a short course (1 week or so) of an oral steroid, such as Prednisone, may be tried, and then the inhaled steroid is tried again. Another type of asthma medication called a leukotriene modifier may also be useful in treating cough variant asthma.
In addition, just as with regular asthma, people with cough variant asthma should take care to avoid things they notice cause their coughing to start up. Common triggers of cough variant asthma are cold air, allergens, and exercise.