Should I do a computed tomography (CT) scan with or without contrast for a patient with persistent asthma?

CT Imaging in Persistent Asthma

For routine management of persistent asthma, CT imaging is generally not indicated—start with chest radiography only if complications are suspected. 1

Initial Imaging Approach

Chest radiography is the appropriate first-line imaging modality when imaging is clinically warranted in asthma patients. 1 The 2025 ACR Appropriateness Criteria explicitly state there is no relevant literature supporting the use of CT (with or without contrast) in the initial imaging of immunocompetent patients with acute asthma exacerbation and low pretest probability of pneumonia. 1

When to Consider Any Imaging

• Suspected life-threatening complications: pneumothorax (0.5-2.5% incidence in status asthmaticus, direct cause of death in 27% of acute exacerbations) or pneumomediastinum 1
• Clinical concern for pneumonia: though incidence is exceedingly low (<2% in uncomplicated asthma exacerbations) 1
• Inability to achieve disease control despite appropriate therapy 2
• Severe deterioration requiring evaluation for underlying structural changes 2

CT Without Contrast: Limited Indications

If CT is deemed necessary, use CT without IV contrast. 1 The ACR guidelines note that CT without contrast may be warranted only in highly specific scenarios:

• Patients who cannot reliably follow-up 1
• Patients for whom any delay in diagnosis could be life-threatening 1
• Only when chest radiograph is negative or equivocal 1
• To evaluate for underlying causes of pneumothorax when radiography is insufficient 1

Why Not Contrast?

There is no literature supporting CT with IV contrast for routine asthma imaging. 1 Contrast is not needed to evaluate:

• Airway wall thickening 3, 4
• Bronchiectasis 3
• Emphysematous changes 3
• Pneumothorax or pneumomediastinum 1

Special Considerations for Severe/Persistent Asthma

Research Context (Not Routine Practice)

While research demonstrates that 80% of severe asthma patients show HRCT abnormalities (bronchial wall thickening 62%, bronchiectasis 40%, emphysema 8%), 3 these findings have limited impact on routine clinical management. 5

Clinical predictors fail to reliably identify structural changes: FEV₁/FVC ratio ≥75% has only 67% sensitivity and 65% specificity for detecting absence of airway structural changes. 3 However, this does not justify routine CT screening.

Current Clinical Role

CT imaging in severe asthma is primarily reserved for: 5

• Excluding comorbid conditions
• Assessing for complications during acute decompensation
• Evaluating patients with persistent symptoms despite maximal therapy when alternative diagnoses are considered

Critical Pitfalls to Avoid

• Do not order routine CT for persistent asthma monitoring—no evidence supports this practice 1
• Do not use CTA (CT angiography) unless pulmonary embolism is specifically suspected 1
• Chest radiography is usually sufficient for pneumothorax diagnosis; reserve CT for cases requiring evaluation of underlying causes 1
• Avoid radiation exposure without clear clinical indication, especially in younger patients with chronic disease requiring longitudinal follow-up

Bottom Line Algorithm

1. No acute complications suspected: No imaging needed
2. Concern for pneumothorax/pneumomediastinum/pneumonia: Start with chest radiography 1
3. Radiograph negative/equivocal AND high clinical suspicion in high-risk patient: Consider CT without contrast 1
4. Routine persistent asthma management: CT not indicated regardless of contrast 1