What tests and treatment should be done for bronchial hyperresponsiveness with chronic cough after a viral infection?

Testing for Bronchial Hyperresponsiveness with Chronic Cough After Viral Infection

Bronchoprovocation challenge (BPC) testing should be performed to evaluate bronchial hyperresponsiveness in patients with chronic cough following a viral infection. 1

Diagnostic Approach

Initial Assessment

• Determine if the cough is subacute (3-8 weeks) or chronic (>8 weeks) after the viral infection
• Subacute cough following a respiratory infection is classified as "postinfectious cough" 1
• If cough persists beyond 8 weeks, consider diagnoses other than postinfectious cough 1

Specific Testing for Bronchial Hyperresponsiveness

1. Methacholine Challenge Test (First-line)

   • Gold standard for detecting bronchial hyperresponsiveness 1
   • High negative predictive value - a negative test essentially excludes asthma 1
   • Positive test indicates bronchial hyperresponsiveness but is not diagnostic of asthma alone 1

2. Spirometry

   • Perform before bronchoprovocation if available
   • Look for reversible airflow obstruction that would indicate asthma 1
   • Normal spirometry does not exclude bronchial hyperresponsiveness 1

3. Induced Sputum Test

   • To evaluate for eosinophilic inflammation 1
   • Helps differentiate between:
     • Asthma (eosinophilic inflammation with bronchial hyperresponsiveness)
     • Non-asthmatic eosinophilic bronchitis (eosinophilic inflammation without bronchial hyperresponsiveness)
     • Postinfectious cough (typically non-eosinophilic) 1

Clinical Significance of Testing Results

• Bronchial hyperresponsiveness has a high positive predictive value for cough variant asthma in non-smoking adults with chronic cough 2
• Postinfectious bronchial hyperresponsiveness is typically transient and resolves within 3 weeks to 3 months 3
• Multiple pathogenic factors may contribute to postinfectious cough, including:
  • Postviral airway inflammation
  • Bronchial hyperresponsiveness
  • Mucus hypersecretion
  • Impaired mucociliary clearance 1

Common Pitfalls to Avoid

• Misdiagnosis: Postviral bronchial hyperresponsiveness syndrome is frequently misdiagnosed as asthma, but it's temporary (3 weeks to 3 months) 3
• Incomplete evaluation: Chronic cough has multiple potential mechanisms that should be systematically evaluated 4
• Overlooking other causes: Upper airway cough syndrome, gastroesophageal reflux, and non-asthmatic eosinophilic bronchitis can coexist with or mimic bronchial hyperresponsiveness 1, 4
• Premature conclusion: A positive bronchoprovocation test alone is not diagnostic of asthma - definitive diagnosis requires resolution of cough with specific antiasthmatic therapy 1

When Testing is Unavailable

If bronchoprovocation challenge testing is not available:

• Consider empiric trial of inhaled ipratropium as first-line treatment for postinfectious cough 5
• If cough persists, consider a trial of inhaled corticosteroids 5
• A positive response to corticosteroids may indicate either asthma or non-asthmatic eosinophilic bronchitis 1

Remember that bronchial hyperresponsiveness testing is essential for accurate diagnosis, appropriate treatment selection, and avoiding unnecessary long-term medication use in patients with postinfectious cough.