What diagnostic tests are used for chronic cough?

Diagnostic Tests for Chronic Cough

A comprehensive diagnostic approach for chronic cough (lasting more than 8 weeks) must include chest radiography and spirometry as mandatory initial tests, followed by targeted investigations based on suspected etiology. 1

Initial Mandatory Investigations

• Chest radiograph - Required for all patients with chronic cough to rule out significant pathology such as malignancy, infection, or structural abnormalities 1
• Spirometry with bronchodilator response - Essential to identify airflow obstruction and assess for reversibility that might indicate asthma 1
• Detailed history and physical examination - Should focus on the common causes of chronic cough and potential aggravating factors 1, 2
• Assessment of cough severity and impact on quality of life - Using validated tools such as cough visual analogue scores or cough-specific quality of life questionnaires 1

Second-Line Investigations (Based on Suspected Etiology)

For Suspected Asthma or Eosinophilic Bronchitis

• Bronchial provocation testing - Should be performed in patients with normal spirometry referred to a respiratory physician 1, 3
• Trial of oral corticosteroids - A two-week trial can help diagnose eosinophilic airway inflammation; lack of response effectively rules it out 1, 3

For Suspected Gastroesophageal Reflux Disease (GERD)

• Empiric treatment trial - Often preferred over diagnostic testing as initial approach 1, 2
• 24-hour esophageal pH monitoring - May be considered if empiric treatment fails 1, 4

For Suspected Upper Airway Cough Syndrome

• Sinus imaging - When rhinosinusitis is suspected based on symptoms 1, 2, 4

For Unexplained Cough After Initial Workup

• High-resolution computed tomography (HRCT) - Useful when other targeted investigations are normal 1, 5
• Bronchoscopy - Should be performed in all patients in whom inhalation of a foreign body is suspected 1, 6

Special Considerations

• ACE inhibitor medication review - All patients on ACE inhibitors should discontinue these medications as they are a common cause of chronic cough 1, 3
• Smoking status assessment - Smoking cessation should be strongly encouraged as it can lead to significant improvement in cough symptoms 1
• Occupational exposure history - A thorough occupational history is essential to identify potential environmental triggers 1

Common Pitfalls to Avoid

• Failure to consider multiple causes - Up to 61.5% of chronic cough cases have multiple etiologies, with the "pathogenic triad" of asthma, postnasal drip syndrome, and GERD accounting for over 90% of cases 4
• Overlooking GERD - Reflux-associated cough may occur without typical gastrointestinal symptoms 1
• Inadequate trial periods for empiric therapy - GERD treatment requires at least 3 months of intensive acid suppression for proper evaluation 1
• Relying solely on spirometry to diagnose asthma - Cough variant asthma may present with normal spirometry 1

Referral to Specialist

• Consider referral to a pulmonologist if the cause of chronic cough remains unidentified after initial evaluation and empiric treatment trials 2, 5
• Chronic cough should only be labeled as idiopathic after thorough assessment at a specialist cough clinic 1