What are the initial diagnostic steps for a patient with a chronic cough?

Initial Diagnostic Steps for Chronic Cough

Chest radiography is the recommended initial diagnostic test for patients with chronic cough lasting more than 8 weeks, with additional testing guided by clinical findings and radiographic results. 1

Initial Assessment Algorithm

Step 1: Chest Radiography

• Chest radiography is recommended by numerous pulmonary and thoracic societies as the first-line imaging test for chronic cough evaluation 1
• The American College of Chest Physicians (ACCP) explicitly includes chest radiography in their chronic cough algorithm 1
• Initial chest radiography has shown clinical efficacy with diagnosis achieved in 82-93% of cases when used as part of standardized clinical protocols 1

Step 2: Clinical History Assessment for Common Causes

• Evaluate for the most common causes of chronic cough, which include:
  • Upper airway cough syndrome (UACS)/post-nasal drip 1
  • Asthma 1, 2
  • Gastroesophageal reflux disease (GERD) 1, 2
  • Chronic bronchitis 3, 2
  • Medication-induced cough (particularly ACE inhibitors) 4, 5

Step 3: Spirometry and Additional Basic Testing

• Perform spirometry to assess for airway obstruction 2
• Measure exhaled nitric oxide and blood eosinophil count to evaluate for eosinophilic inflammation 2
• Use validated instruments to measure cough severity and quality of life 4, 2

When to Consider Advanced Imaging

High-Resolution CT (HRCT)

• HRCT should be performed only in selected patients with abnormal chest radiographs or when initial evaluation and empiric treatment fail 1
• Studies show that wide application of chest CT in all patients with chronic cough may be of low clinical yield 1
• Chest CT has shown positive predictive value of 90% when used in patients with suspected underlying pulmonary disease 1
• Most common CT findings in chronic cough with normal radiographs are bronchiectasis (28%) and bronchial wall thickening (21%) 1

When to Avoid Advanced Imaging

• Routine chest CT is not recommended for initial evaluation of chronic cough 1
• In one study, 17 patients who underwent chest CT without clinical indication had no findings relevant to their management 1
• There is no relevant literature supporting the use of FDG-PET/CT or MRI chest in the initial evaluation of chronic cough 1

Red Flags Requiring More Urgent/Extensive Evaluation

• Hemoptysis 4
• Smoker >45 years with new cough or change in cough pattern 4
• Prominent dyspnea, especially at rest or night 4
• Hoarseness accompanying the cough 4
• Systemic symptoms (fever, weight loss) 4
• Trouble swallowing, vomiting, or recurrent pneumonia 4

Common Pitfalls to Avoid

• Failing to recognize red flags that require in-person evaluation 4
• Not using validated cough severity tools to objectively assess symptoms 4, 2
• Inappropriate use of antibiotics for viral or post-infectious cough 4
• Overlooking medication-induced causes, particularly ACE inhibitors 4, 5
• Delaying diagnosis by not following a systematic approach 1, 2

Special Considerations

• Up to one-fourth of patients with chronic cough have multiple contributing causes 3
• Chest radiography has limitations in detecting certain conditions like bronchiectasis, with studies showing up to 34% of CT-proven bronchiectasis cases had unremarkable chest radiographs 1
• If initial evaluation and empiric treatment fail, consider referral to specialty care for additional testing 1, 2