What is the appropriate evaluation and management for a child who has had a cough for three weeks?

Evaluation and Management of 3-Week Cough in Children

For a child with 3 weeks of cough, initiate watchful waiting with supportive care and schedule reassessment at the 4-week mark, as most post-viral coughs resolve spontaneously by 3 weeks, but persistent cough beyond 4 weeks requires systematic evaluation with chest radiograph and spirometry. 1, 2

Initial Classification at 3 Weeks

At 3 weeks duration, this represents subacute cough that has not yet reached the threshold for chronic cough (defined as ≥4 weeks in children ≤14 years). 1, 2

• Approximately 90% of viral-related coughs resolve by day 21, though 10% may persist beyond 25 days. 1, 2
• The most common etiology at this timeframe is persistent post-viral inflammation causing postnasal drip, upper airway irritation, mucus hypersecretion, or transient bronchial hyperresponsiveness. 2

Critical History and Physical Examination Elements

Determine if this is "specific" versus "non-specific" cough by evaluating for the following red flags: 1

Specific Cough Pointers Requiring Immediate Investigation:

• Wet/productive cough (suggests protracted bacterial bronchitis or suppurative lung disease) 1, 3
• Coughing with feeding (suggests aspiration or swallowing dysfunction) 1, 4
• Digital clubbing (suggests chronic suppurative lung disease, bronchiectasis, or cystic fibrosis) 1, 5
• Failure to thrive or weight loss (suggests serious underlying disease including TB or cystic fibrosis) 1, 5
• Hemoptysis (requires urgent evaluation) 5
• Paroxysmal cough with post-tussive vomiting or inspiratory "whoop" (suggests pertussis, which has 80% secondary attack rate in susceptible contacts) 2

Environmental and Contextual Factors:

• Tobacco smoke exposure in the home (exacerbates and prolongs cough) 1, 2
• Vaccination status for pertussis (unvaccinated children have median cough duration of 52-61 days versus 29-39 days in vaccinated) 1
• Geographic setting (TB, parasitic diseases more common in resource-poor countries) 1

Management Strategy at 3 Weeks

For Non-Specific Dry Cough (No Red Flags):

Implement watchful waiting with the following supportive measures: 2

• Minimize environmental irritants, especially tobacco smoke exposure 1, 2
• Ensure adequate hydration to thin secretions 4
• Avoid over-the-counter cough and cold medications in children under 6 years due to lack of efficacy and risk of adverse events 2, 4
• Schedule mandatory follow-up at 4 weeks if cough persists 2, 5

For Specific Cough (Red Flags Present):

Do not wait—initiate evaluation immediately: 1

• Wet/productive cough: Consider protracted bacterial bronchitis and obtain chest radiograph. If clinical suspicion is high, may initiate 2-week antibiotic course targeting Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis (amoxicillin or amoxicillin-clavulanate as first-line). 1, 4, 3

• Paroxysmal cough with pertussis features: Obtain nasopharyngeal aspirate or swab for culture/PCR and initiate macrolide antibiotics (azithromycin or erythromycin) even before confirmation. 2

• Other specific pointers: Obtain chest radiograph and consider referral to pediatric pulmonology for further investigation including possible bronchoscopy, especially in infants <18 months. 1, 6

Critical Pitfalls to Avoid

• Do NOT empirically treat for asthma based on cough alone—cough sensitivity and specificity for asthma is poor, and most children with isolated chronic cough do not have asthma. 1, 4
• Do NOT empirically treat for GERD or upper airway cough syndrome unless specific clinical features support these diagnoses. 1, 4
• Do NOT dismiss as "post-viral" without proper follow-up, as 18% of children with chronic cough algorithms had serious progressive respiratory illness including bronchiectasis, aspiration lung disease, or cystic fibrosis. 1, 5
• Do NOT use antihistamines or β-agonists for acute/subacute viral cough—they are non-beneficial and have adverse events. 1, 4

Mandatory Actions at 4-Week Mark

If cough persists to 4 weeks, this becomes chronic cough requiring systematic evaluation: 1, 5

• Obtain chest radiograph to identify structural abnormalities, pneumonia, foreign body, TB, or bronchiectasis 1, 5
• Perform spirometry (pre- and post-bronchodilator) if child is ≥6 years old and able to perform reliably 1, 5
• Use pediatric-specific cough algorithm based on whether cough is wet/productive versus dry 1, 4
• Consider referral to pediatric pulmonology if initial evaluation reveals concerning findings or if diagnosis remains unclear 1, 6

Age-Specific Considerations

Common etiologies differ significantly between children and adults—do not presume adult causes (chronic bronchitis, COPD, GERD, upper airway cough syndrome) apply to children. 1 The pediatric differential includes protracted bacterial bronchitis, retained foreign body, aspiration lung disease, congenital anomalies, and early bronchiectasis, which require different diagnostic approaches. 1, 3