Chronic cough: Which tests should precede referral to a specialist?

Dr Imran Satia is an assistant professor in the Division of Respirology at McMaster University.

Which investigations should be performed in patients with chronic cough before referring them to a specialist center?

Thank you very much for the question. It’s a very important question. And before I answer that, I think it’s very important to first understand and take a very, very good detailed history, because that will determine what investigations need to be done as a second step. So, it’s important that physicians take a history about the cough, the type of cough. Is it a productive cough or a dry cough? Is that coughing up blood? Is there any associated shortness of breath, wheeze, or chest tightness? Have there been any fevers, or weight loss, or night sweats? And also, take a good medical history and a drug history, including for medications like ramipril or lisinopril, which are commonly used blood pressure medications that are called angiotensin-converting enzyme inhibitors (ACEIs), and also take an important history related to smoking, and now also vaping.

But if all of these things have been done, then the 3 most important tests that the family physician should do before referring to a specialist are to do a basic blood test called the full blood count or complete blood count (CBC) to check for the blood eosinophil count. If the blood eosinophil count is raised, then that might raise some suspicion that this could be asthma or even nonasthmatic eosinophilic bronchitis.

[The] second [thing] to do is a chest x-ray to make sure that there’s no evidence of any infection or any malignancy, or any structural or lung disease like pulmonary fibrosis or even bronchiectasis; or even if there’s any heart disease, to see any evidence of what we call pulmonary edema or pulmonary congestion, because these can easily be treated with treatments specific for those conditions.

The other important thing is a simple breathing test called spirometry. And if available, then you should also do something called a reversibility assessment by giving 2 puffs of a short-acting beta₂-agonist and then repeating the spirometry to see whether or not there’s what we call reversible airways disease, which could be helpful to diagnose asthma.

In summary, there are 3 important tests: chest x-ray, spirometry/reversibility [tests], and a blood test to check for CBC. And that’s after doing a detailed history.