A person with cough-variant asthma (CVA), often has a dry cough, but they don’t actually 'cough anything up'.
They may not have other common asthma symptoms, such as wheezing or shortness of breath.
The coughing can disrupt sleep at night and can be made worse by exercise and other triggers, such as dust, perfumes, and cold air.
Anyone can get cough-variant asthma at any time, but it is common in young children with childhood asthma. Cough-variant asthma may lead to the development of other asthma symptoms.
What causes cough-variant asthma?
Like “classic” or “typical” asthma, no one really knows what causes cough-variant asthma. However, coughing may start after people are exposed to allergens, or when they are breathing in cold air. Coughing may also follow an upper respiratory infection. For example, sinusitis with asthma is common.
In addition, a cough that begins after a person has begun taking beta-blockers is likely to be cough-variant asthma. Beta-blockers are drugs used to treat high blood pressure, heart disease, heart failure, migraines, palpitations, and other conditions. Beta-blockers are also found in eye drops to treat glaucoma. These eye drops can bring on asthma symptoms, including cough. Asthma and aspirin-sensitivity is another cause of coughing with asthma.
How is cough-variant asthma diagnosed?
Cough-variant asthma is somewhat difficult to diagnose because the cough may be the only symptom, and the cough itself may appear to be bronchitis or a cough associated with postnasal drip.
Your GP will ask you questions about your medical history and will examine you and listen to you breathe. However, people with cough-variant asthma often have normal physical examinations, chest X-rays, peak flow measurements and spirometry. Spirometry involves measuring how much air you can exhale after first taking a deep breath, and how quickly you can empty your lungs. The asthma test uses a device called a spirometer to do the measuring.
A methacholine challenge test - also known as a histamine challenge test - will indicate asthma, but it may require the use of a special facility. This test may be performed if your symptoms and spirometry test do not clearly show asthma. When inhaled, methacholine causes the airways to spasm and narrow if asthma is present. During the test, you inhale increasing amounts of methacholine aerosol mist before and after spirometry. The methacholine test is considered positive - meaning that asthma is present - if the lung function drops by at least 20 per cent. A bronchodilator (airway-opening drug) is always given at the end of the test to reverse the effects of the methacholine.
Another way to diagnose cough-variant asthma involves treatment. The GP may choose to give the patient standard asthma treatments. If the cough responds to these types of treatments, a diagnosis of cough-variant asthma can be made.
How is cough-variant asthma treated?
Cough-variant asthma is treated in the same way that typical asthma is treated. You may be given an asthma inhaler with salbutamol, ipratropium, and/or inhaled steroids (anti-inflammatory agents). You should see a gradual improvement in asthma symptoms over six to eight weeks.