Should CT Chest Be Performed?
Yes, chest CT should be performed in this patient with chronic cough, negative chest X-ray, and negative EGD, as the negative predictive value of chest radiography is only 64% for excluding pulmonary causes of chronic cough. 1
Evidence Supporting CT Imaging in This Clinical Scenario
The American College of Radiology guidelines indicate that chest CT is appropriate when common causes have been excluded or empirically treated without resolution 2, 3. Since this patient has already undergone EGD (addressing gastroesophageal reflux disease as a potential cause), further evaluation with CT is warranted 2.
Key Supporting Data
In patients with chronic cough and normal chest X-ray, CT reveals clinically relevant abnormalities in 36% of cases, with the most common findings being bronchiectasis (11.9%), bronchial wall thickening (10.2%), and mediastinal lymphadenopathy (8.5%) 1.
The negative predictive value of chest radiography is only 64%, meaning that a normal chest X-ray fails to exclude significant pulmonary pathology in more than one-third of patients 1.
Studies demonstrate that chest radiography has relatively low specificity (approximately 82%) for detecting abnormalities relevant to chronic cough 4.
Clinical Algorithm for CT Decision-Making
Indications Present in This Patient:
- Failed empirical treatment: The negative EGD suggests GERD has been investigated, implying other common causes have been addressed 2, 3
- Persistent symptoms beyond 8 weeks (by definition of chronic cough) 2, 3
- Normal chest X-ray with ongoing symptoms warrants advanced imaging to detect structural abnormalities not visible on plain radiography 2, 1
What CT Will Evaluate:
- Bronchiectasis: The reference standard for noninvasive diagnosis, present in up to 20% of elderly patients and often asymptomatic 2, 3
- Interstitial lung disease: Early manifestations may not be visible on chest X-ray 2, 3
- Bronchial wall thickening and airway abnormalities: Well-visualized on non-contrast CT 3
- Occult malignancy: 1-2% of chronic cough patients have underlying malignancy 2
Important Caveats and Clinical Context
Selective vs. Routine Use
While the American College of Radiology emphasizes that CT should be selective rather than routine 4, 2, this patient meets criteria for selective use given the negative workup thus far. Studies show that when CT is performed without clinical suspicion in an algorithmic fashion, findings may not be relevant to management in many cases 4. However, when performed based on clinical suspicion or failed empirical treatment, the yield is substantially higher 4.
Age-Related Considerations
If this patient is elderly (>65-70 years), be aware that chronic pulmonary changes on CT may represent age-related findings rather than the cause of current symptoms 2. Up to 20% of patients over 70 have bronchiectasis, with 57% being asymptomatic 2. This doesn't negate the need for CT, but interpretation must consider clinical context 2.
Timing and Follow-up
The American College of Radiology recommends CT after empirical treatment of common causes has failed 2, 3. Since EGD has been performed (addressing GERD), and assuming other common causes (upper airway cough syndrome, asthma) have been empirically treated, CT is now appropriate 2, 5.
Recommended CT Protocol
Order non-contrast chest CT, as this is adequate for evaluating the most common abnormalities associated with chronic cough (bronchiectasis, bronchial wall thickening, interstitial lung disease) 3. Contrast is not necessary unless there is specific suspicion for vascular abnormalities or mediastinal pathology 3.
Common Pitfalls to Avoid
- Don't delay CT indefinitely in patients with persistent symptoms after negative initial workup, as the sensitivity of chest X-ray is insufficient 1
- Don't assume normal chest X-ray excludes significant pulmonary pathology - one-third of patients will have relevant CT findings 1
- Don't order CT before addressing common causes (upper airway cough syndrome, asthma, GERD) unless red flag symptoms are present 4, 2
- Don't dismiss CT findings in elderly patients as purely age-related without clinical correlation, as they may represent treatable causes of cough 2