Cough

08 June 2015

Diagnosing a chronic cough

Any cough lasting longer than 8 weeks warrants investigation particularly if you have any of the warning signs and you should expect to possibly undergo some investigations.

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A chronic cough is slightly less common than an acute cough but can afflict up to 10 – 18% of the population at any one time.  Typically it is more common in women and this may be related to the increased sensitivity of the cough reflex in women. 

A chronic cough certainly merits investigation as to the underlying cause. Unfortunately in up to 40% of cases no obvious cause for the cough can be found thus resulting in a very frustrating process for both you as the patient as well as for the clinician.

A thorough history and examination by your physician may help to elucidate some the causes of a chronic cough. One the biggest causes for a chronic cough is smoking yet it is alarmingly surprising how many smokers seek attention for their cough while they continue to smoke! Furthermore, a chronic cough may be a sign of emphysema with up to half of all emphysema patients reporting a daily cough.

Certain blood pressure medication which contain ACE-inhibitors such as captopril, enalapril ( Capotenâ, Pharmapressâ) are well known to cause a dry, irritating cough which goes away once the medication has been substituted with another anti-hypertensive drug.
 

Other factors on history that may help with the diagnosis is

  • the timing of the cough, certainly a nocturnal cough with significant variability i.e. worse in winter than summer, worse in early mornings, would suggest a diagnosis of asthma.
  • Reflux symptoms with episodes of hoarse voice may suggest reflux disease.
  • Significant nasal symptoms such as nasal stuffiness & itchiness, frequent ‘throat-clearing’ as well as sensation of nasal secretions dripping down the back of the throat may suggest the entity of the ‘post-nasal drip’ now referred to as the Upper Airway Cough Syndrome (UACS).
  • In some instances that acute cough of a recent viral upper respiratory tract infection may persist longer than 8 weeks in what is known as reactive or ‘twitchy’ airways due to an increased sensitivity of the cough reflex.


Tests used to diagnose chronic cough

Chest X-ray:
Certainly a chest X-ray is warranted in the setting of a chronic cough. Though no-one likes to think of the diagnosis of cancer, lung cancer is certainly a cause of a chronic cough and should be considered. A chest X-ray may help to gives clues to other diagnoses as well including tuberculosis which is common in South Africa. When there is associated ongoing loss of weight, drenching night sweats and fevers, TB must be considered. Though not diagnostic, a chest X-ray will also give clues to either causes such as emphysema / COPD and other rarer forms of lung disease such as interstitial lung disease.

Lung function testing:  is a much-neglected tool in the assessment of a chronic cough. This relatively simple exercise involves blowing into a simple device, which records a number of values to work out your lung volumes.  Much like testing your blood sugar for diabetes or cholesterol, this simple test should be done on all chronic cough patients. Only with lung function testing can you make the accurate diagnosis of asthma, emphysema and COPD.

A battery of other investigations such as skin prick testing, gastroscopy, bronchoscopy, CT scanning, ECG & exercise testing, blood tests may have a role to play all in helping to make the diagnosis of a chronic cough though will depend on the associated symptoms and signs. 

Compiled February 2011 by Dr. Greg Symons [MB. ChB, DipPEC, FCP (SA), Cert. Pulm. (SA)], Consultant Pulmonologist, Division of Pulmonology, Department of Medicine, Groote Schuur Hospital & Clinical Researcher, UCT Lung Institute (Pty) Ltd www.lunginstitute.co.zain George Street, Mowbray. Contact the UCT Lung Institute on ph 021 406 6850. 

 

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Cough Expert

Professor Keertan Dheda has received several prestigious awards including the 2014 Oppenheimer Award, and has published over 160 peer-reviewed papers and holds 3 patents related to new TB diagnostic or infection control technologies. He serves on the editorial board of the journals PLoS One, the International Journal of Tuberculosis and Lung Disease, American Journal of Respiratory and Critical Medicine, Lancet Respiratory Diseases and Nature Scientific Reports, amongst others. Read his full biography at the University of Cape Town Lung Institute.

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