Chronic cough

Chronic cough is defined as cough lasting more than 8 weeks. In adults with a normal chest X-ray and no smoking history, >90% of cases are caused by upper-airway cough syndrome (post-nasal drip from allergic or non-allergic rhinitis / sinusitis), asthma or cough-variant asthma (cough without classic wheezing), and gastro-oesophageal reflux disease (GORD). The 'big three' workup empirically treats these in sequence. Outside that profile the differential widens: ACE-inhibitor-induced cough (10-20% of users; resolves in weeks after stopping), chronic bronchitis (smokers), eosinophilic bronchitis (allergic but no asthma), bronchiectasis (purulent sputum), tuberculosis (high-risk populations), pertussis (paroxysmal, 100-day cough), interstitial lung disease, lung cancer (smokers >40 with weight loss, haemoptysis), heart failure (orthopnoea, dyspnoea), psychogenic cough.

• Upper-airway cough syndrome (post-nasal drip) — most common; allergic / non-allergic rhinitis, sinusitis.
• Asthma / cough-variant asthma — exercise- or cold-air-triggered; spirometry with bronchodilator response confirms.
• GORD — worse lying down, after meals; may have no heartburn.
• ACE inhibitor — dry cough in 10-20% of users; resolves 1-4 weeks after stopping.
• Chronic bronchitis — smokers, productive cough most days for 3+ months.
• Bronchiectasis — daily purulent sputum, recurrent infections.
• Tuberculosis — weight loss, night sweats, haemoptysis, risk factor exposure.
• Pertussis (whooping cough) — paroxysmal, post-tussive vomiting, 'whoop' on inspiration.
• Lung cancer — new cough or change in chronic cough in smokers >40, haemoptysis.
• Heart failure — nocturnal cough, orthopnoea, peripheral oedema.
• Eosinophilic bronchitis — like asthma but normal spirometry.

Chest X-ray + spirometry are first-line. CRP / ESR for inflammatory clues. Full blood count (eosinophilia → atopy / eosinophilic bronchitis). LFTs if heart failure is plausible. Sputum culture + AFB if TB risk. Mediora.AI is most useful for the bloodwork (rule out anaemia driving heart-failure cough; check inflammation); the diagnostic workup is chest imaging + spirometry + clinical history.