Chronic Cough Evaluation
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Direct answer
A cough persisting beyond eight weeks in an adult — with a chest radiograph taken, smoking addressed and any ACE inhibitor stopped — is chronic cough, and in India the first duty is excluding tuberculosis with sputum microscopy or NAAT before the benign triad. Worldwide, three causes dominate after that gate: upper airway cough syndrome (post-nasal drip from rhinitis or sinusitis), cough-variant asthma and non-asthmatic eosinophilic bronchitis (both steroid-responsive, often invisible on plain spirometry), and gastro-oesophageal reflux disease — together accounting for most radiograph-negative chronic cough. Evaluation runs chest radiograph, then spirometry with bronchodilator response, then sequential empirical trials, with red flags — haemoptysis, weight loss, smoker over 45, hoarseness — fast-tracking CT and bronchoscopy.
What you must remember
- Definition and prerequisites: over eight weeks' duration, chest radiograph reviewed, smoker status documented, ACE inhibitor withdrawn for at least four weeks before labelling.
- The Indian gate first: under the National TB Elimination Programme, any cough of two weeks or more in a presumptive TB case warrants sputum AFB or NAAT (CBNAAT) — chronic cough at eight weeks has already passed that threshold; post-tuberculous bronchiectasis is a large Indian cough reservoir.
- Upper airway cough syndrome: throat clearing, drip sensation, cobblestoning; trial of intranasal corticosteroid plus antihistamine for two to four weeks.
- Cough-variant asthma and non-asthmatic eosinophilic bronchitis: nocturnal and trigger-driven cough with normal spirometry; demonstrate with methacholine challenge, raised FeNO or sputum eosinophils; both respond to inhaled corticosteroids.
- Reflux cough: may be non-acid and silent; an eight-to-twelve-week proton pump inhibitor trial with lifestyle measures, failing which impedance-pH studies and reflux-focused referral.
- ACE inhibitor cough: bradykinin-mediated, affects up to a tenth or more of users, appears within weeks (or later), resolves one to four weeks after stopping — the cheapest diagnostic test in the topic.
- Red flags mandating imaging beyond radiograph: haemoptysis, weight loss, night sweats, smoker over 45, hoarseness, clubbing, lymphadenopathy.
- Refractory cough: after the big three and imaging, consider post-infectious cough, pertussis in adults, and neuromodulator therapy (gabapentin, amitriptyline) via specialist cough clinics.
Working through eight weeks of cough
A 45-year-old non-smoking woman has coughed for three months; the radiograph is normal and she takes no medications. Step one — the Indian gate: two sputum samples for AFB or a single NAAT; both negative closes the tuberculosis door for now. Step two — history geography: drips, wheeze, or heartburn do not always announce themselves, so ask about throat clearing in the morning, cough with cold air or laughter, and nocturnal symptoms. Step three — physiology: spirometry with bronchodilator response is normal, so order FeNO and, if available, methacholine challenge; a positive challenge with high FeNO reframes her as cough-variant asthma, and eight weeks of inhaled corticosteroid is both diagnostic and therapeutic. Step four — sequential trials: if the challenge is negative, treat the nose next (intranasal steroid plus antihistamine for a month), then the oesophagus (PPI trial with nocturnal and dietary measures for two to three months). Step five — escalate on failure or red flag: HRCT thorax, bronchoscopy if any localising feature, and only then the refractory-cough pathway.
The reasoning to articulate: in chronic cough the therapeutic trial is the investigation — each cause has a cheap, time-boxed probe, and the discipline lies in giving each long enough and one at a time.
Where students slip
The first slip is skipping the gate: in India, treating a cough-variant-asthma protocol onto undiagnosed tuberculosis wastes months and spreads disease; the programme's two-week rule exists precisely for that trap. The second is the reflex chest CT for a clean history and radiograph — sequencing matters, and empirical trials of the big three come first in the algorithm taught in Indian medical colleges. The third is forgetting ACE inhibitors, including combination tablets patients do not report as "BP medicines". Local flavour earns marks: biomass-fuel smoke exposure in women who cook on chulhas, an occupational history (dusts, cold air in cold-storage workers), adult pertussis now recognised in India, and the post-COVID cough that follows viral clearance. Dextromethorphan and codeine syrups bought over the counter suppress nothing chronic.
Frequently asked questions
How is chronic cough defined?
Cough persisting beyond eight weeks in an adult, after chest radiograph, smoking assessment and ACE inhibitor withdrawal.
What is the first investigation in the Indian setting?
Sputum for AFB or NAAT to exclude tuberculosis — the National TB Elimination Programme applies this to any cough of two weeks or more.
Which three causes dominate radiograph-negative chronic cough?
Upper airway cough syndrome, cough-variant asthma with non-asthmatic eosinophilic bronchitis, and gastro-oesophageal reflux disease.
What is the role of the empirical therapeutic trial?
Each cause has a time-boxed trial — intranasal steroid, inhaled corticosteroid, proton pump inhibitor — given sequentially, because response is both diagnostic and curative.
When does chronic cough mandate CT and bronchoscopy?
Immediately with red flags: haemoptysis, weight loss, smoker over 45, hoarseness, clubbing, or any localising sign despite a normal radiograph.