Your medical history and physical examination help determine which tests your doctor will order. The goal of testing is to identify the underlying cause of your chronic cough.
Rather than testing, many doctors will try treating you for one of the common causes of chronic cough. Only if the treatments aren't successful will they begin testing for more unusual causes.
- X-rays. Although a routine chest X-ray won't reveal the most common reasons for a cough postnasal drip, acid reflux or asthma it may be used to check for lung cancer and pneumonia and other lung diseases. An X-ray of your sinuses may reveal evidence of a sinus infection.
- Computerized tomography (CT) scans. CT scans also may be used to check your sinus cavities for pockets of infection.
Lung function tests
These simple, noninvasive tests measure how much air your lungs can hold and how fast you can exhale. This test is required to diagnose asthma. Sometimes you may also have an asthma challenge test, which checks how well you can breathe before and after inhaling a drug called methacholine (Provocholine).
If the mucus that you cough up is discolored, your doctor may want to test a sample of it for bacteria.
If your doctor isn't able to find an explanation for your cough, special scope tests may be considered to look for rare causes. These tests use a thin, flexible tube equipped with a light and camera to visualize structures within your body. This equipment can be inserted into your windpipe (trachea) and bronchi to look for abnormalities, as well as biopsy the inside lining of your airway (mucosa) to look for any cellular abnormalities.
A chest X-ray and a spirometry test, at a minimum, are recommended to evaluate the cause of a chronic cough in a child.