In a 4-year-old boy with atopic eczema and recurrent cough following an upper respiratory infection, what is the most appropriate next investigation?

Most Appropriate Next Investigation

For this 4-year-old boy with recurrent cough following an upper respiratory infection, a chest X-ray is the most appropriate next investigation. 1

Rationale for Chest Radiography

The CHEST guidelines provide clear, Grade 1B recommendations that all children aged ≤14 years with chronic cough (defined as >4 weeks duration) should undergo chest radiography as a mandatory initial investigation. 1 While the question states "days" of cough following the current URTI, the history of a similar episode "a few weeks ago" suggests a pattern of recurrent or potentially chronic cough that warrants systematic evaluation.

Key Diagnostic Considerations

• Chest radiography has an infinite positive likelihood ratio for detecting abnormalities when present, making it excellent for ruling in disease, though it cannot rule out conditions like asthma when normal. 1

• The chest X-ray will help identify:

  • Structural lung abnormalities 1
  • Pneumonia or infiltrates 1
  • Foreign body aspiration 1
  • Signs of bronchiectasis or other chronic lung disease 1

• In a child with atopic eczema (a marker of atopic predisposition), recurrent respiratory symptoms warrant objective investigation rather than empirical treatment. 1

Why Other Options Are Less Appropriate

Spirometry (Option B)

• Spirometry is recommended for children with chronic cough, BUT only when age-appropriate (typically >6 years, sometimes >3 years with trained personnel). 1
• At 4 years old, this child is too young to reliably perform spirometry, making chest X-ray the primary investigation. 1
• Spirometry would be considered if the child were older and able to cooperate with the test. 1

CT Scan (Option C)

• CT scanning is NOT recommended as a routine investigation for chronic cough in children. 1
• The CHEST guidelines explicitly state (Grade 1B): "We recommend not routinely performing additional tests (eg, chest CT); these should be individualized and undertaken in accordance with the clinical setting and the child's clinical symptoms and signs." 1
• CT would only be considered after initial chest X-ray if specific concerning findings warrant further imaging. 1

Bronchoscopy (Option D)

• Bronchoscopy is NOT a first-line investigation for chronic cough in children. 1
• Like CT scanning, bronchoscopy should only be performed when clinically indicated based on specific findings, not as a routine test. 1
• It would be considered only after initial investigations (chest X-ray, spirometry when age-appropriate) reveal concerning features requiring direct visualization. 1

Antihistamine Trial

• Antihistamines are non-beneficial for acute cough in children and should not be used empirically. 2
• The European Respiratory Society guidelines explicitly recommend against diagnosing asthma based on symptoms alone and state that "children with chronic cough as the only symptom are unlikely to have asthma." 1
• Empirical treatment for asthma, upper airway cough syndrome, or other conditions should NOT be used unless specific features consistent with these conditions are present (Grade 1A recommendation). 1

Clinical Algorithm for This Patient

1. Obtain chest radiograph immediately as the first-line investigation 1

2. Assess cough characteristics: Determine if the cough is wet/productive versus dry, as this guides subsequent management 1

3. Look for specific "cough pointers" that suggest serious underlying disease:

   • Coughing with feeding 1
   • Digital clubbing 1
   • Failure to thrive 1
   • Chest deformity 1

4. Evaluate environmental factors, particularly tobacco smoke exposure, which should be eliminated immediately 1, 2

5. Based on chest X-ray results and cough characteristics:

   • If wet/productive cough with normal X-ray: Consider 2-week antibiotic trial for protracted bacterial bronchitis 1
   • If dry cough with normal X-ray and features of asthma (wheeze, atopy): Consider asthma evaluation 1
   • If abnormal X-ray: Pursue specific findings with appropriate specialist referral 1

Important Caveats

• The atopic eczema history increases this child's risk for developing asthma, but asthma cannot be diagnosed on cough alone without objective evidence of airway obstruction or wheeze. 1

• Recurrent URTIs do not protect against atopic disease and may actually be associated with increased risk of polysensitization and atopic dermatitis. 3

• If pertussis is suspected (paroxysmal cough, post-tussive vomiting, known contact), specific testing for Bordetella pertussis should be undertaken. 1

• Over-the-counter cough and cold medications should NOT be used in children under 6 years due to lack of efficacy and potential toxicity. 2