In active and former smokers with CT detected emphysema but without airway obstruction, the presence of an abnormal DLco is associated with a worse clinical presentation

Rationale: Little is known about the impact of an abnormal DLco ( Objective: To compare clinical and functional characteristics of active or former smokers without airway obstruction with or without emphysema and/or abnormal DLco. Methods: This is an observational study of active or former smokers that underwent a low dose CT scan (LDCT), pulmonary function tests, COPD assessment test (CAT) and 6 minute walking distance test (6MWD) . Patients were classified in 3 groups depending on the presence of visually detected radiological emphysema and DLco values (no-emphysema; emphysema with DLcou003e80%; emphysema with DLco Results: 168 patients were analyzed. Patients with emphysema had a higher CAT score (7.96 vs 5.95 p=0.002) and a greater fall in SpO2% post-6MWD (22.7% vs 4.2%, p=0,004) . In those with an abnormal DLco, CAT score are even higher (4.78 vs 9.36, p=0.01) and a greater % having a fall in the SpO2% (96.3% vs 94.4%, p=0.007). In this group there were more active smokers (69% vs. 50%, p=0.025), with lower mean predicted FEV1 (96.7 vs 105.2%, p=0.004) and higher residual volume/total lung capacity ratio (37.05 vs 32.44, p:0.05). Conclusion: In active or former smokers with emphysema, the presence of an abnormal DLco determine a worse clinical and physiological presentation. The present findings gives value to the determination of DLco in smokers without airway obstruction.