While cough may accompany the usual symptoms associated with asthma, in cough variant asthma, cough alone may be a precursor to or the sole symptom in an asthmatic. When cough is the only asthma symptom, this is known as cough variant asthma (CVA).
What is Cough Variant Asthma?The main symptom of CVA is a chronic, non-productive cough. These asthma patients have cough as the main or only symptom of their asthma. These patients are a small percentage of total asthma patients. CVA patients are, however, a distinct group rather than merely being thought of as 'coughing asthmatics.'
CVA patients have some differences from patients with typical asthma. For example, while normal asthmatics do not differ from healthy volunteers in their cough relex, CVA patients have a more sensitive cough reflex. Interestingly, CVA patients have a smaller reaction to methacholine challenge testing compared to other asthmatics.
How Is Cough Variant Asthma Diagnosed?Because cough is a common symptom for asthma, your provider may order spirometry. If spirometry demonstrates reversible obstruction, your provider may start a therapeutic trial for asthma. However, asthmatics may have a normal lung exam and spirometry creating a 'diagnostic dilemma,' where your doctor may suspect, but is unable to prove, you have asthma.
In this case, your provider may preform methacholine challenge testing in-order to demonstrate bronchial hyperresponsiveness and diagnose asthma. If a methacholine challenge test does not produce hyperresponsiveness, it is unlikely that asthma is the cause of a cough. A definitive diagnose can be made if the cough symptoms respond after asthma treatment.
How Is Cough Variant Asthma Treated?
Treatment of CVA is virtually the same as for asthma. Partial improvement of cough may be seen as quickly as 1 week with bronchodilators like Albuterol, but may not completely resolve for up to 8 weeks after starting an inhaled steroid like Flovent.
If the cough only partially resolves, your provider may try a more potent steroid like oral prednisone. Alternatively, your provider may do special tests to identify eosinophils, a marker of inflammation, in your lung. If eosinophils are present in the lung, Zafirlukast has been shown improve cough among patients with CVA and has been beneficial in CVA patients without a good response to inhaled steroids.
A small group of patients may experience worsening of the cough with inhaled steroids due to the aersols used in the inhaler device. Alternatively, if the cough worsens, it is important that it is not another condition, like GERD, causing the symptoms.
Dicpinigaitis, Peter V. Accessed May 1, 2009. Chronic Cough Due to Asthma: ACCP Evidence-Based Clinical Practice Guidelines