In a patient with mild emphysema identified on a CT scan, should pulmonary function testing (PFT) be performed?

Yes, perform PFT in patients with mild emphysema on CT scan

You should perform pulmonary function testing (PFT) in patients with mild emphysema identified on CT scan to confirm the diagnosis of COPD, assess functional impairment, and guide management decisions. 1

Rationale for PFT After CT Findings

The 2025 GOLD guidelines emphasize that spirometry remains essential to confirm the presence of airflow obstruction and therefore to diagnose COPD 1. While CT scanning can identify structural emphysema, it cannot replace functional assessment for several critical reasons:

Key Diagnostic Gaps Without PFT

• CT detects structure, not function: Emphysema visible on CT represents anatomical damage but doesn't quantify the physiologic impact on airflow or gas exchange
• 21% of patients with significant emphysema (>7%) have no airflow obstruction on spirometry 2, meaning they don't meet diagnostic criteria for COPD despite structural changes
• Management guidelines are based on post-bronchodilator spirometry values: Most treatment studies used post-BD measurements as inclusion criteria, so applying these recommendations requires functional confirmation 1

The Diagnostic Algorithm

When CT shows mild emphysema and clinical suspicion for COPD is high:

1. Start with pre-bronchodilator spirometry as an initial screening test 1
2. If pre-BD FEV1/FVC <0.7: Perform post-BD spirometry to confirm COPD diagnosis 1
3. If pre-BD FEV1/FVC ≥0.7 but clinical suspicion remains high: Still perform post-BD testing, as volume responders can have discordant ratios (pre-BD ≥0.7 but post-BD <0.7) 1
4. Include DLCO measurement: This is particularly valuable as diffusing capacity can detect the mildest degrees of alveolar destruction that may not be apparent even on high-resolution CT 3

Important Caveats

CT may be more sensitive than PFT for detecting mild emphysema 4, but this creates a clinical dilemma: research shows 69% of patients with CT evidence of emphysema lack functional findings of emphysema 4. These patients may represent:

• Very early disease requiring surveillance
• Structural changes without clinically significant functional impairment
• Candidates for aggressive risk factor modification (smoking cessation)

The presence of visual emphysema on CT in smokers without spirometric COPD (GOLD stage 0) predicts disease progression 5, with greater decline in FEV1/FVC ratio and progression of quantitative emphysema over 5 years compared to those without CT emphysema.

Clinical Implications

Performing PFT after finding mild emphysema on CT allows you to:

• Establish baseline lung function for future comparison
• Identify airflow obstruction that warrants COPD treatment
• Detect gas exchange abnormalities through DLCO that may not correlate with emphysema severity 2
• Risk stratify for disease progression and guide follow-up intervals 1
• Avoid overdiagnosis: Not all CT emphysema equals functional COPD requiring pharmacotherapy

If initial spirometry is normal but CT shows emphysema and clinical suspicion is high, the GOLD 2025 report recommends follow-up with repeat testing at intervals 1, as these patients are at increased risk of developing COPD.