Patients with chronic obstructive pulmonary disease (COPD) who had a lower diffusing capacity of the lung for carbon monoxide (DLCO) had worse clinical outcomes, according to the results of a study published in CHEST.

Researchers conducted an analysis of participants who were part of the COPDGene study (ClinicalTrials.gov Identifier: NCT00608764) and who also participated in the 5-year follow-up visit. They analyzed pulmonary function testing, quality of life, symptoms, exercise performance, and exacerbation rates.  DLCO percent predicted was primarily analyzed as a continuous variable and additionally categorized into 4 groups: DLCO and forced expiratory volume in 1 second (FEV1) >50% (control), only DLCO ≤50%, only FEV1 ≤50%, and both FEV1 and DLCO ≤50%. Clinical outcomes were compared among groups.

Among the 1806 participants of the COPDGene 5-year visit, 1564 had sufficient data available to include in the analysis. Lower percent predicted DLCO was associated with increased COPD morbidity, including symptoms and quality of life (COPD Assessment Test: 0.53; P <.001; St. George’s Respiratory Questionnaire: 1.67; P <.001; Medical Outcomes Study Short Form 36-item physical functioning: -0.89; P <.001), exercise performance (6-minute walking distance: -45.35; P <.001), and severe COPD exacerbations (1.14; P <.001), independent of FEV1.

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However, the independent effect of DLCO tended to be less intense than the effect of FEV1 for all other outcomes, but was still within a clinically relevant range.

“This study demonstrates that DLCO measurement, a readily available, frequently obtained test, provides clinically relevant information beyond spirometry and [computed tomographic] evidence of emphysema,” the researchers wrote. “Specifically, DLCO measurement may provide information regarding functional status and identify subgroups of patients who display diminished exercise performance or frequent exacerbations that are incompletely captured by existing indices.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Balasubramanian A, MacIntyre NR, Henderson RJ, et al. Diffusing capacity of carbon monoxide in assessment of chronic obstructive pulmonary disease [published July 25, 2019]. CHEST. doi:10.1016/j.chest.2019.06.035