Cough is the most common complaint observed in respiratory clinics. A persistent cough may have both physiological morbidity and a psychological burden on the patient.

For decades, cough variant asthma (CVA), eosinophilic bronchitis (EB), upper airway cough syndrome (UACS) (formerly called postnasal drip syndrome), and gastroesophageal reflux-related cough (GERC) are regarded to be the common causes of chronic cough. The prognosis of the treatment rests upon the correct diagnosis and subsequent treatment.

Chronic cough may be diagnosed by-

• spirometry, 
• bronchial challenge testing, 
• induced sputum test for differential cells, and 
• 24-hour oesophagal pH value monitoring. 

Lia K. et al published a study describing the characteristics of different cough, concomitant symptoms, and medical history in diagnosing the causes of chronic cough.

The highlights of the study are-

• CVA is frequently associated with nocturnal cough.
• Asthma is less frequently associated with nocturnal cough.
• Asthma is frequently associated with Rhinitis.
• rhinitis is also generally related to UACS and some EB
• History of Rhinitis seems to be a clinical feature for diagnosing eosinophilia-related cough due to eosinophilic inflammation.
• GERC is mostly associated with at least 1 reflux-related symptom.
• Foods may elevate reflux and the symptoms of gastroesophageal reflux may worsen after meals.
• Heartburn should be considered a “rule in” for diagnosing GERC. 
• Cough after meals is also a good “rule in” symptom of GERC.
• UAC/ postnasal drip syndrome is characterized by a sensation of postnasal dripping, nasal discharge, throat clearing, runny nose, nasal itching, and nasal congestion. Although these features can be found associated with other causes as well.
• UACS is a “rule out” if an adult patient does not present with rhinitis/sinusitis-related symptoms.

These points add to the diagnosis of the aetiology of cough and thus serve as a useful guide for the empiric treatment of chronic cough. This will further add to the current scenario of the covid-19 situation where investigations are nearly inaccessible for the routine cough patients.

Lastly, the study also highlights the treatment regimen for the chronic cough according to the established diagnosis-

• Corticosteroids or other antiasthmatic could be the drug of choice for nocturnal cough; 
• Antireflux treatment (proton pump inhibitor with prokinetic agents) could be the drug of choice for patients with reflux symptoms or cough after meals or exclude other common cause of chronic cough; 
• Treatment for UACS should be initiated if a patient shows symptoms of postnasal dripping, a history of sinusitis, and/or rhinitis/sinusitis-related symptoms.

Source:Lai, K, Zhan, W, Li, H, Yi, F, Peng, W, Zhou, J. et al. The Predicative Clinical Features Associated with Chronic Cough That Has a Single Underlying Cause, The Journal of Allergy and Clinical Immunology: In Practice, 2021;9(1):426-432. https://doi.org/10.1016/j.jaip.2020.06.066.