Predicting Mortality in COPD: Diffusing Capacity vs BODE Index

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Is diffusing capacity an effective predictor of mortality among patients with COPD, either together with or independent of the BODE index?

All-cause mortality in individuals with COPD was strongly predicted by diffusing capacity (DLCO), independent of computed tomography (CT) evidence of emphysema and airway wall thickness and BODE index, according to study findings published recently in the Annals of the American Thoracic Society.

The standard for assessing mortality risk in COPD is the BODE index, a multidimensional scoring system and capacity measure that includes body mass index, forced expiratory volume in 1 second (FEV1), 6-minute walk distance, and dyspnea score. Researchers sought to evaluate DLCO as a predictor of mortality among patients with COPD, with DLCO used both independently and together with the BODE index.

The researchers conducted time-to-event analyses among 2329 patients with COPD (former/current smokers with FEV1/FVC <0.7) and DLCO measurements who were participants in the COPDGene study (ClinicalTrials.gov Identifier: NCT00608764). Survival was modeled, adjusting for sex, age, smoking status, pack-years, BODE index, CT percent emphysema (low attenuation areas <-950 Hounsfield units), history of cardiovascular or kidney diseases, and CT airway wall thickness using Cox proportional hazard methods.

Researchers discovered that 378 (16.8%) patients died during the follow-up period (median 4.9 years). Mortality increased by 29% for every 10% decrease in DLCO percent predicted (hazard ratio 1.29; 95% CI, 1.17-1.41; P <.001). DLCO percent predicted produced similar results to BODE (C-statistic DLCO 0.68, BODE 0.70) when compared with other clinical predictors. Moreover, adding DLCO to BODE improved discriminative accuracy (C-statistic 0.71).


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Key study limitations include the lower-than-average mortality rate among clinical trial participants, residual confounding, lack of a validation cohort, and the small sample size for cause-of-death analysis.

These findings “support inclusion of DLCO in prognostic models for COPD,” said researchers. “In the context of a growing interest in deep phenotyping and precision medicine in COPD, a simple minimal-risk measurement of gas transfer offers important prognostic information that should be considered in assessing and managing COPD patients,” the researchers noted.

Disclosure: This research was part of the COPDGene study, which is supported by AstraZeneca, Bayer Pharmaceuticals, Boehringer-Ingelheim, Genentech, GlaxoSmithKline, Novartis, Pfizer, and Sunovion.

Reference

Balasubramanian A, Putcha N, MacIntyre NR, et al. Diffusing capacity and mortality in chronic obstructive pulmonary disease. Ann Am Thorac Soc. Published online August 15, 2022. doi:10.1513/AnnalsATS.202203-226OC

This article originally appeared on Pulmonology Advisor