What tests should be ordered for a patient with persistent cough and shortness of breath?

Testing for Persistent Cough and Shortness of Breath

All patients with persistent cough and shortness of breath require chest radiography and spirometry with bronchodilator testing as mandatory initial investigations. 1, 2, 3

Mandatory First-Line Testing

Chest Radiograph

• Essential for ruling out pneumonia, malignancy, structural abnormalities, tuberculosis, and infiltrative diseases that could explain both cough and dyspnea 1, 2, 3, 4
• Particularly important when abnormal vital signs are present (tachypnea, tachycardia, fever ≥38°C) 1

Spirometry with Bronchodilator Response

• Required to identify airflow obstruction and assess for reversibility suggesting asthma 1, 2, 3
• Critical because cough-variant asthma commonly presents with normal baseline spirometry 2, 5
• Helps distinguish obstructive patterns (asthma, chronic bronchitis) from restrictive patterns (fibrosis, sarcoidosis) 4

Clinical Assessment

• Measure vital signs including respiratory rate, heart rate, oxygen saturation, and blood pressure 3
• Document medication history, specifically ACE inhibitors (common reversible cause) and beta-blockers (may exacerbate asthma) 1, 2, 3, 6
• Obtain detailed occupational and environmental exposure history 1, 2
• Assess smoking status, as smoking is a dose-related common cause of persistent cough 1, 2

Second-Line Testing Based on Initial Results

If Spirometry is Normal but Asthma Suspected

• Bronchial provocation testing (methacholine challenge) should be performed in patients referred to respiratory physicians with chronic cough and normal spirometry 1, 2
• A two-week trial of oral corticosteroids effectively rules out eosinophilic airway inflammation if no response occurs 1, 2

If Upper Airway Symptoms Present

• Consider trial of topical corticosteroid for rhinosinusitis 1
• No specific testing required initially; diagnosis based on clinical response 6

If GERD Suspected (or No Clear Diagnosis After Above)

• Empiric treatment trial is preferred over diagnostic testing as the initial approach 1, 2
• 24-hour esophageal pH monitoring may be considered if empiric treatment fails, though interpretation criteria remain controversial 1
• Important: GERD-related cough often occurs without gastrointestinal symptoms, making it a commonly missed diagnosis 1, 2

Additional Testing for Acute Presentations

C-Reactive Protein (CRP)

• Suggested when pneumonia is suspected, as CRP ≥30 mg/L combined with fever, dyspnea, and chest signs strengthens pneumonia diagnosis 1
• CRP <10 mg/L makes pneumonia less likely in acute cough 1

Procalcitonin

• Not recommended for routine use in suspected pneumonia 1

Microbiological Testing

• Not routinely needed unless results would change therapy 1
• Consider nasopharyngeal culture or swab for pertussis if cough ≥2 weeks with paroxysms, post-tussive vomiting, or inspiratory whooping 1

Critical Action Items Before Further Testing

• All patients on ACE inhibitors must discontinue these medications immediately, as they are a common and reversible cause 1, 2, 3, 6
• Strongly encourage smoking cessation, which leads to significant cough improvement 1, 2

Common Pitfalls to Avoid

• Do not overlook GERD as it frequently presents without typical heartburn or regurgitation symptoms 1, 2
• Do not rely solely on normal spirometry to exclude asthma, as cough-variant asthma commonly has normal baseline lung function 2, 5
• Do not order extensive testing for acute cough without first completing basic evaluation (history, exam, chest X-ray, spirometry) 4, 7
• Ensure adequate treatment trial duration: GERD requires at least 3 months of intensive acid suppression before concluding treatment failure 1, 2

When to Consider Advanced Testing

High-Resolution CT

• May be useful when targeted investigations are normal in chronic cough 1
• Indicated if red flag symptoms present: hemoptysis, weight loss, recurrent pneumonia, or persistent symptoms despite optimal treatment 5

Bronchoscopy

• Should be undertaken when foreign body inhalation is suspected 1
• Consider if initial workup negative and symptoms persist 7

Referral Considerations

• Chronic cough should only be labeled idiopathic after thorough assessment at a specialist cough clinic 1, 2
• Refer to pulmonologist if cause not identified after completing systematic evaluation 6, 5