What is the appropriate evaluation and management approach for a patient with a chronic cough lasting greater than 1 month, considering potential underlying causes such as respiratory conditions, allergies, or infections?

Evaluation and Management of Chronic Cough (>1 Month)

Begin with a chest radiograph and discontinue any ACE inhibitor immediately—then systematically treat the three most common causes (upper airway cough syndrome, asthma, and GERD) sequentially and additively, as multiple causes often coexist. 1, 2

Initial Assessment and Red Flags

Immediate Actions

• Obtain a chest radiograph in all patients with chronic cough to rule out serious pathology including lung cancer, tuberculosis, bronchiectasis, and other structural abnormalities 1, 2
• Stop ACE inhibitors immediately if the patient is taking one, regardless of when it was started—resolution typically occurs within days to 2 weeks (median 26 days) 2
• If the patient smokes, smoking cessation is the priority intervention before pursuing other diagnoses, as most achieve resolution within 4 weeks 2

Red Flags Requiring Direct Investigation (Not Empiric Treatment)

• Hemoptysis 1, 2
• Significant dyspnea or respiratory distress 1, 2
• Fever or systemic symptoms 1, 2
• Unintentional weight loss 1, 2
• History of cancer, tuberculosis, or AIDS 2
• Chest radiograph showing mass, infiltrate, or other concerning findings 2
• Finger clubbing on examination 1

The Three Common Causes (Account for >90% of Cases)

1. Upper Airway Cough Syndrome (UACS) - Most Common (~44%)

Clinical clues: Sensation of postnasal drip, throat clearing, nasal discharge, or rhinosinusitis symptoms (though physical exam and sinus imaging may be normal) 1, 3

Treatment approach:

• First-generation antihistamine plus decongestant (e.g., diphenhydramine or chlorpheniramine with pseudoephedrine) for several weeks 1, 4
• This combination decreases cough severity and hastens resolution 4
• Response typically occurs within 1-2 weeks if UACS is the cause 1

2. Asthma (Including Cough-Variant Asthma and Eosinophilic Bronchitis)

Clinical clues: Cough may be the only symptom—wheezing and dyspnea are often absent 1, 2

Diagnostic approach:

• Perform spirometry in all patients 1
• Normal spirometry does NOT exclude asthma—many patients with cough-variant asthma lack sufficient reversibility to meet traditional criteria 1, 2
• Bronchoprovocation testing can confirm diagnosis if baseline spirometry is normal 3

Treatment approach:

• Initiate inhaled corticosteroids with or without bronchodilators empirically, even without spirometric evidence of obstruction 2
• Consider a trial of oral prednisolone (30-40 mg daily for a short course) if inhaled therapy fails 1
• Allow several weeks for adequate treatment response 2

3. Gastroesophageal Reflux Disease (GERD)

Clinical clues: Heartburn, regurgitation, or sour taste—but cough may be the only manifestation 1, 2

Treatment approach:

• Initiate intensive acid suppression therapy (high-dose PPI twice daily) for at least 3 months 2
• GERD is frequently overlooked in general respiratory clinics 2
• Response may take longer than UACS or asthma (≥3 months required) 2

Sequential and Additive Treatment Strategy

Critical principle: More than one cause is present in the majority of patients 1

1. Start with empiric treatment for the most likely cause based on history 1, 2
2. If partial response occurs, add treatment for the next most likely cause rather than stopping the first treatment 1
3. Continue this sequential, additive approach until cough resolves 1
4. Allow adequate treatment duration before declaring failure: weeks for UACS/asthma, ≥3 months for GERD 2

When Initial Empiric Treatment Fails

Before Ordering Advanced Testing

• Confirm adequate treatment duration and dosing for all three common causes 2
• Verify medication adherence 1
• Re-evaluate for ACE inhibitor use or smoking 2

Advanced Diagnostic Testing

• Proceed to high-resolution CT (HRCT) only after sequential empiric treatment for all three common causes has failed 2
• HRCT identifies abnormalities in up to 42% of patients with normal chest radiographs and is diagnostic in 24% 2
• HRCT is the reference standard for detecting bronchiectasis, which accounts for up to 8% of chronic cough cases and may be missed on plain radiography 2

Bronchoscopy Indications

• Perform bronchoscopy to evaluate for occult airway disease (endobronchial tumor, sarcoidosis, suppurative infection, eosinophilic or lymphocytic bronchitis) if HRCT and empiric treatment fail 1

Less Common Causes to Consider

After Common Causes Are Addressed

• Pertussis infection: Consider if paroxysmal cough, post-tussive vomiting, or inspiratory whoop present—obtain nasopharyngeal culture or PCR 1
• Chronic bronchitis/COPD: Typically associated with sputum production and dyspnea in smokers 1
• Bronchiectasis: May present as "dry" bronchiectasis without sputum—look for history of prior respiratory insult 1
• Lung cancer: Fourth most common presenting feature—consider especially in smokers with risk factors 1
• Nonacid reflux, swallowing disorders, congestive heart failure, habit cough: Consider based on clinical findings 1

Common Pitfalls to Avoid

• Do not rely on cough characteristics or timing for diagnosis—they have little diagnostic value 1
• Do not order extensive upfront testing—sequential empiric treatment is more cost-effective than comprehensive initial investigation 2
• Do not use single PEF measurements or PEF for bronchodilator response—they are less accurate than FEV1 1
• Do not stop the first treatment when adding a second—additive therapy is crucial 1
• Do not diagnose "unexplained cough" until uncommon causes have been ruled out and referral to a cough specialist has been considered 1

Timeframe Definitions

• Acute cough: <3 weeks 1
• Subacute cough: 3-8 weeks 1, 4
• Chronic cough: >8 weeks in adults, >4 weeks in children 1, 4, 5