How to differentiate and manage acute vs chronic cough in a patient, considering potential underlying conditions such as Chronic Obstructive Pulmonary Disease (COPD) or immunocompromised status?

Acute vs Chronic Cough: Differentiation and Management

Duration-Based Classification

Classify cough by duration to guide your entire diagnostic and treatment approach: acute cough lasts <3 weeks, subacute cough lasts 3-8 weeks, and chronic cough lasts >8 weeks. 1, 2

• This temporal classification is the critical first step that determines all subsequent management decisions 1, 2
• The 3-8 week "gray zone" represents subacute cough, often postinfectious in nature 1

Initial Red Flag Assessment

Before proceeding with algorithmic management, immediately rule out life-threatening conditions including pneumonia, pulmonary embolism, respiratory distress, hemoptysis, weight loss, night sweats, or history of cancer/TB/AIDS. 2, 3

• Obtain chest radiography if pneumonia is suspected based on tachypnea, abnormal lung findings, or hypoxemia 4, 2
• Check for ACE inhibitor use and discontinue immediately if present—this is a common reversible cause 4, 2, 5
• Assess smoking status and counsel on cessation, as smoking exacerbates cough 4, 2

Management of Acute Cough (<3 Weeks)

For acute cough from viral upper respiratory infection, treat with first-generation antihistamine/decongestant combination, naproxen, adequate hydration, and honey for cough suppression. 1, 3

• Acute cough is most commonly caused by viral URTI and is typically self-limiting within 2 weeks 1, 3
• Avoid antibiotics for viral causes—they are not indicated 2, 3
• Consider empiric antibiotics only if bacterial pneumonia is suspected based on clinical findings 3
• For asthma or COPD exacerbations presenting with acute cough, use inhaled bronchodilators and systemic corticosteroids 3

Management of Subacute Cough (3-8 Weeks)

Determine if subacute cough is postinfectious or non-infectious, as this guides treatment: postinfectious cough responds to antihistamine/decongestant combinations, while non-infectious subacute cough should be managed as chronic cough. 1, 4

• Postinfectious cough mechanisms include persistent postnasal drip, upper airway irritation, or transient bronchial hyperresponsiveness 1
• For upper airway cough syndrome (UACS), use first-generation antihistamine/decongestant combination as initial treatment 4, 2
• If asthma is suspected, perform spirometry or bronchoprovocation challenge; if unavailable, trial inhaled bronchodilators and corticosteroids empirically 4
• Consider pertussis in the differential diagnosis for subacute cough 4, 6

Management of Chronic Cough (>8 Weeks)

Use sequential and additive empiric therapy for chronic cough because multiple causes frequently coexist—treat UACS first, then asthma, then GERD, maintaining all partially effective treatments. 1, 2

Step 1: Upper Airway Cough Syndrome (UACS)

• Start with first-generation oral antihistamine/decongestant combination 1, 2
• UACS (formerly postnasal drip syndrome) is one of the three most common causes accounting for 90% of chronic cough cases 7, 8

Step 2: Asthma

• Do not rely on medical history alone to rule asthma in or out—perform spirometry or bronchoprovocation challenge 2, 5
• Treat with inhaled bronchodilators and inhaled corticosteroids 1, 2
• Asthma can cause chronic cough even without typical wheezing symptoms 7, 5

Step 3: Gastroesophageal Reflux Disease (GERD)

• Initiate intensive acid suppression with proton pump inhibitors for a minimum of 2 months 1
• GERD is one of the three most common causes and often coexists with other conditions 7, 8
• Empiric treatment should be initiated even without typical reflux symptoms 5

Step 4: Non-Asthmatic Eosinophilic Bronchitis (NAEB)

• Treat with inhaled corticosteroids 1, 4
• Consider induced sputum testing for eosinophils if available 4

Critical Pitfalls to Avoid

Never rely on cough characteristics (timing, quality, productive vs nonproductive) for diagnosis—they lack diagnostic sensitivity and specificity. 1, 2, 8

• A detailed history of cough character, timing, and complications has been shown to have no predictive value for determining the cause 8
• Do not treat only one cause—use sequential and additive therapy as multiple etiologies frequently coexist in 59% of cases 2, 8
• Do not diagnose idiopathic cough prematurely—this is a diagnosis of exclusion requiring thorough evaluation and failed treatment trials first 2
• Do not suppress cough when clearance is important, such as in pneumonia or bronchiectasis 2

Special Populations

Immunocompromised Patients

• Maintain high suspicion for opportunistic infections and atypical pathogens 3
• Lower threshold for chest radiography and advanced imaging 2

COPD Patients

• Acute cough often represents exacerbation requiring bronchodilators and systemic corticosteroids 3
• Chronic cough in COPD should still be evaluated systematically for other contributing causes 7

Refractory Chronic Cough

If cough persists despite appropriate sequential treatment, consider high-resolution CT scan and bronchoscopy, and refer to pulmonology or otolaryngology. 4, 2, 7

• Treatment options for idiopathic cough include dextromethorphan, baclofen, nebulized local anesthetics, low-dose morphine, gabapentin, pregabalin, and speech therapy 2, 7
• Dextromethorphan should not be used if cough occurs with smoking, asthma, emphysema, or excessive phlegm production 9