What diagnostic tests are recommended for an 8-year-old child with a persistent wet cough and initial fever?

Diagnostic Tests for an 8-Year-Old with Persistent Wet Cough and Initial Fever

For an 8-year-old child with a wet cough that began with fever and remains persistent, a chest radiograph and spirometry (pre- and post-β2 agonist) should be the initial diagnostic tests performed. 1

Initial Diagnostic Approach

• A chest radiograph is recommended as the first-line investigation for all children with chronic wet cough (>4 weeks duration) 1
• For an 8-year-old child, spirometry testing (pre- and post-β2 agonist) should be performed as they are old enough to reliably complete the test 1
• Assessment of cough characteristics is essential - wet/productive cough suggests possible protracted bacterial bronchitis (PBB) or other specific diagnoses 1
• Determine if the cough has persisted for more than 4 weeks, which would classify it as chronic and require a systematic diagnostic approach 1, 2

Additional Tests Based on Clinical Findings

• If pertussis is clinically suspected (paroxysmal cough with post-tussive vomiting or inspiratory "whoop"), specific tests for Bordetella pertussis infection should be performed 1, 2
• For children with wet cough and specific "cough pointers" (digital clubbing, chest deformity, growth failure), more extensive testing is warranted 1, 2
• If the initial chest radiograph or spirometry shows abnormalities, further investigations should be guided by these findings 1

Management Algorithm Based on Test Results

1. Normal chest radiograph and spirometry with wet cough:

   • Prescribe 2 weeks of antibiotics targeted to common respiratory bacteria (Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis) 1, 2
   • If cough resolves within 2 weeks, diagnose as protracted bacterial bronchitis (PBB) 1
   • If cough persists after initial 2-week course, prescribe an additional 2-week course of appropriate antibiotics 1

2. Persistent wet cough after 4 weeks of appropriate antibiotics:

   • Refer to a pediatric pulmonologist for further assessment 1, 3
   • Consider additional investigations including flexible bronchoscopy with bronchoalveolar lavage for quantitative cultures 1, 3
   • Consider chest CT imaging to evaluate for possible bronchiectasis 1, 3

Tests to Avoid

• Do not routinely perform additional tests such as skin prick tests, Mantoux tests, bronchoscopy, or chest CT scans unless specifically indicated by clinical findings 1, 4
• Avoid empirical treatment approaches without appropriate diagnostic testing 1
• Over-the-counter cough suppressants should not be used in children under 6 years and are generally not recommended for wet/productive cough at any age 5

Important Considerations

• Wet cough that persists beyond 4 weeks should never be dismissed as "just a cold" and requires active management 2, 6
• Early intervention with appropriate antibiotics may prevent progression to bronchiectasis in children with protracted bacterial bronchitis 2, 3
• The most common diagnoses in children with chronic wet cough are protracted bacterial bronchitis and bronchiectasis 6, 3
• Environmental factors, particularly tobacco smoke exposure, should be assessed as they can exacerbate cough symptoms 1, 2

Red Flags Requiring Immediate Medical Attention

• Development of high fever (≥39°C/102.2°F) during the course of illness 2
• Signs of respiratory distress (increased respiratory rate, retractions, grunting) 2
• Change in sputum color to yellow/green (purulent) without improvement on treatment 2
• Development of specific cough pointers such as digital clubbing, chest deformity, or failure to thrive 1, 2