Differential diagnosis

1. Chronic bronchitis / COPD

• Usually cigarette smoking, biomass-fuel smoke, air pollution, or occupational dust exposure
• Mucoid sputum, worse in mornings and winter
• Wheeze, exertional breathlessness, recurrent infective exacerbations
• Confirm airflow obstruction with spirometry

2. Bronchiectasis

• Daily chronic cough with moderate to large volumes of mucopurulent, sometimes foul-smelling sputum
• Recurrent chest infections, dyspnea, wheeze, hemoptysis, crackles or clubbing
• Causes include previous severe pneumonia, tuberculosis, cystic fibrosis, allergic bronchopulmonary aspergillosis, immune deficiency, ciliary disorders, and nontuberculous mycobacterial infection.
• HRCT chest is the diagnostic test of choice. Textbook of Family Medicine 9e, p. 270.

3. Pulmonary tuberculosis

• Chronic productive cough with low-grade fever, night sweats, weight loss, anorexia, hemoptysis, and TB contact or endemic-area exposure
• Consider sputum AFB smear/culture or molecular testing and chest radiograph.

4. Chronic infection or suppurative lung disease

• Recurrent bacterial bronchitis, lung abscess, chronic aspiration, or nontuberculous mycobacterial pulmonary disease
• Foul purulent sputum, fever, weight loss, recurrent consolidation, or aspiration risk suggests this group.

5. Asthma, including cough-variant asthma

• Episodic wheeze, chest tightness, nocturnal or early-morning symptoms, triggers such as dust, cold air, exercise, or allergens
• Sputum can occur, particularly with poorly controlled asthma or eosinophilic airway disease.

6. Upper-airway cough syndrome

• Nasal blockage, rhinorrhea, throat clearing, sensation of nasal secretions draining into throat
• Chronic rhinosinusitis or allergic rhinitis may coexist with productive cough.

7. Gastroesophageal reflux disease or chronic aspiration

• Heartburn, sour regurgitation, hoarseness, cough after meals or when lying down
• Can produce cough through reflux and microaspiration, and may aggravate asthma or bronchiectasis.

8. Lung cancer or endobronchial lesion

• Especially in smokers or older adults
• New or changing chronic cough, hemoptysis, weight loss, chest pain, hoarseness, recurrent pneumonia in the same location, or clubbing are concerning.

9. Interstitial lung disease and other chronic lung disorders

• Idiopathic pulmonary fibrosis, sarcoidosis, pneumoconiosis, and hypersensitivity pneumonitis
• Usually dry cough, but sputum may coexist because of smoking, infection, bronchiectasis, or reflux.
• Occupational history is important: silica, coal dust, asbestos, farming/mold exposure, etc.

10. Cardiac causes

• Left ventricular failure or pulmonary edema: cough worse when lying flat, paroxysmal nocturnal dyspnea, edema, orthopnea, basal crackles, sometimes frothy sputum.

11. Medication and irritant-related cough

• ACE inhibitors usually cause a dry cough but can coexist with another sputum-producing disorder.
• Tobacco smoke, vaping, biomass smoke, workplace chemicals, and ambient air pollution can sustain chronic airway inflammation.

12. Less common causes

• Foreign body or airway obstruction
• Tracheobronchomalacia
• Chronic pulmonary embolic disease
• Immunodeficiency with recurrent lower respiratory infections
• Cystic fibrosis or primary ciliary dyskinesia, especially if symptoms began in childhood or there is recurrent sinus/ear disease or infertility.

High-yield clinical clues

Initial evaluation

1. Detailed history: smoking, sputum volume/color/odor, hemoptysis, fever, weight loss, TB exposure, asthma/allergy, reflux, medications, occupation, and recurrent infections.
2. Examination: wheeze, crackles, clubbing, lymph nodes, signs of heart failure.
3. Chest radiograph and spirometry are key initial tests in chronic cough. Textbook of Family Medicine 9e, p. 310.
4. Depending on findings: sputum Gram stain/culture, AFB/NAAT testing, CBC, HRCT chest for bronchiectasis or interstitial disease, and bronchoscopy if obstruction, cancer, or persistent unexplained hemoptysis is suspected.