Can computed tomography and carbon monoxide transfer coefficient diagnose an asthma-like phenotype in COPD?

BACKGROUND AND OBJECTIVE: Post-mortem and computed tomography (CT) studies indicated that emphysema is a feature of COPD even in the 'blue bloater/chronic bronchitis' type. We aim to test the hypothesis that the non-emphysematous patients are distinct from the main body of COPD and are more akin to asthmatic patients.

METHODS: We studied 54 patients with COPD. Emphysema was measured by Goddard's visual scoring of CT scan and the carbon monoxide transfer coefficient (KCO). Bronchial biopsy was offered for thickness of basement membrane (BM) (≥7 µm) as a marker of remodelling in irreversible asthma. Spirometry was repeated after therapy with Budesonide/Formoterol for 1 year.

RESULTS: The non-emphysematous phenotype were 24 of 54 patients (44%) by CT scan and 23 of 54 patients (43%) by KCO, showing agreement in 53 out of 54 patients. The non-emphysematous patients were younger, had higher forced expiratory volume in 1 s (FEV1 ) (median 61% vs 49.7%), greater prevalence of hypertrophy of nasal turbinates and higher serum IgE. The emphysematous phenotype had lower BMI and greater dyspnoea score. The BM was thickened in 11 of 14 and 0 of 10 patients in the non-emphysematous and emphysematous groups, respectively. Three patients without emphysema and a normal BM normalized their FEV1 upon receiving inhaled corticosteroid (ICS)/long-acting β2 agonist (LABA). All the non-emphysematous improved their FEV1 after ICS/LABA (median = 215 mL). The median decline in the emphysematous was -65 mL.

CONCLUSION: The non-emphysematous phenotype of COPD displays important features of asthma: clinical picture, histology and response to ICS. CT and KCO can predict spirometric response to ICS/LABA.