A novel CT-emphysema index/FEV₁ approach of phenotyping COPD to predict mortality

Abstract

Background

COPD-associated mortality was examined using a novel approach of phenotyping COPD based on computed tomography (CT)-emphysema index from quantitative CT (QCT) and post-bronchodilator (BD) forced expiratory volume in 1 second (FEV₁) in a local Malaysian cohort.

Patients and methods

Prospectively collected data of 112 eligible COPD subjects (mean age, 67 years; male, 93%; mean post-BD FEV₁, 45.7%) was available for mortality analysis. Median follow-up time was 1,000 days (range, 60–1,400). QCT and clinicodemographic data were collected at study entry. Based on CT-emphysema index and post-BD FEV₁% predicted, subjects were categorized into “emphysema-dominant,” “airway-dominant,” “mild mixed airway-emphysema,” and “severe mixed airway-emphysema” diseases.

Results

Sixteen patients (14.2%) died of COPD-associated causes. There were 29 (25.9%) “mild mixed,” 23 (20.5%) “airway-dominant,” 15 (13.4%) “emphysema-dominant,” and 45 (40.2%) “severe mixed” cases. “Mild mixed” disease was proportionately more in Global Initiative for Chronic Obstructive Lung Disease (GOLD) Group A, while “severe mixed” disease was proportionately more in GOLD Groups B and D. Kaplan–Meier survival estimates showed increased mortality risk with “severe mixed” disease (log rank test, p=0.03) but not with GOLD groups (p=0.08). Univariate Cox proportionate hazard analysis showed that age, body mass index, long-term oxygen therapy, FEV₁, forced volume capacity, COPD Assessment Test score, modified Medical Research Council score, St Georges’ Respiratory Questionnaire score, CT-emphysema index, and “severe mixed” disease (vs “mild mixed” disease) were associated with mortality. Multivariate Cox analysis showed that age, body mass index, and COPD Assessment Test score remain independently associated with mortality.

Conclusion

“Severe mixed airway-emphysema” disease may predict COPD-associated mortality. Age, body mass index, and COPD Assessment Test score remain as key mortality risk factors in our cohort.

Keywords:

• computed tomography
• emphysema
• forced expiratory volume
• COPD
• mortality

Acknowledgments

The authors wish to thank the National Institute of Health, Ministry of Health Malaysia, for the provision of research grant to conduct this study, and Loh Guan Lye Specialist Centre, Penang for providing the service of CT and blood collection for this research. This paper was presented at the 22nd Congress of the Asian Pacific Society of Respirology, Sydney, Australia, November 23–26, 2017 (Oral Presentation, “Late Breaking Findings” Session) and the abstract was published in Respirology. 2017;22(Suppl 3):70–71 (Abstract no AOL 012).

Disclosure

The authors report no conflicts of interest in this work.