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Articles

Disproportionally Impaired Diffusion Capacity Relative to Airflow Limitation in COPD

ORCID Icon, ORCID Icon, ORCID Icon, , , , , & show all
Pages 627-634 | Received 10 Sep 2020, Accepted 29 Oct 2020, Published online: 23 Nov 2020
 

Abstract

Forced expiratory volume in 1 s (FEV1) is a standard physiological index of chronic obstructive pulmonary disease (COPD), but reflects emphysema and vascular abnormalities less sensitively than diffusion capacity for carbon monoxide (DLCO). This study tested whether a disproportionally impaired DLCO relative to FEV1 (FEV1 z-score>-3 and DLCO z-score≤-3) is a common functional COPD phenotype associated with distinct clinical and structural features and the prognosis of two cohorts. The cross-sectional analyses of the Korea COPD Subgroup Study (KOCOSS) cohort (multicenter study in Korea) included 743 males with COPD whose DLCO was available. The cross-sectional and longitudinal analyses of the Kyoto University Cohort (single-center study in Japan) included 195 males with COPD who were prospectively followed for 10 years. A disproportionally impaired DLCO relative to FEV1 was observed in 29% and 31% of patients in the KOCOSS and Kyoto University cohorts, respectively. In the multivariable analysis, the disproportionally impaired DLCO was associated with worse symptoms, shorter 6-minute walking distance, paraseptal and centrilobular emphysema on computed tomography, and reduced arterial oxygen and carbon dioxide pressures compared to the reference (FEV1 z-score>-3 and DLCO z-score>-3). In the multivariable Cox proportional hazard model, a higher long-term mortality was observed in the disproportionally impaired DLCO group than in the reference group (hazard ratio [95% confidence interval] = 3.09 [1.52–6.29]) and similar to the DLCO z-score≤-3 and FEV1 z-score≤-3 group. The disproportionally impaired DLCO relative to FEV1 is common and associated with increased symptoms, emphysema, arterial blood gas abnormalities, and increased long-term mortality in patients with COPD.

Disclosure statement

The authors report no conflicts of interest in this work.

Additional information

Funding

The Kyoto University Cohort was partially supported by the Japan Society for the Promotion of Science (JSPS) [Grants-in-Aid for scientific research 19K08624, 16K09536, 25461156, 21590964, and 16390234]. The KOCOSS cohort was funded by Research of Korea Centers for Disease Control and Prevention [2016ER670102 and 2018ER670100].

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