We are delighted to present a new article recently published in the European Respiratory Journal by a multi-centre international authorship, including our team at UCL/H.
Mortality surrogates in combined pulmonary fibrosis and emphysema
Context: Idiopathic pulmonary fibrosis (IPF) can coexist with emphysema, forming a condition called combined pulmonary fibrosis and emphysema (CPFE), which might lead to a slower decline in forced vital capacity (FVC) compared to IPF without emphysema. Our study aimed to explore the connection between mortality and lung function markers of disease progression in two groups of IPF patients.
Approach: We identified CPFE patients by assessing the presence of visual emphysema on computed tomography (CT) scans. These patients were divided into groups based on different thresholds of emphysema presence (10% or 15% visual emphysema) and using a machine learning model that considered both emphysema and interstitial lung disease extents. We compared the characteristics at the beginning of the study, the decline in forced vital capacity (FVC) and diffusing capacity of the lung for carbon monoxide (DLco) over one year (using specific statistical models), and how these factors related to mortality using Cox regression models, between non-CPFE and CPFE subgroups.
Findings: In both sets of IPF patients, those with CPFE and 10% or more emphysema had a higher history of smoking and lower initial DLco compared to CPFE patients with less than 10% emphysema. When analysing patients with 10% or more emphysema, the decline in DLco over one year was more strongly linked to mortality than the decline in FVC. These findings were consistent even when considering patients eligible for IPF treatment trials and when categorizing subjects by 15% emphysema or using unsupervised machine learning. Importantly, this machine learning method helped identify CPFE patients where FVC decline was not strongly associated with mortality. In non-CPFE IPF patients, declines of 5% or more and 10% or more in FVC over one year were strongly linked to mortality.
Conclusion: When monitoring disease progression in IPF, it’s important to consider DLco decline in patients with 10% or more emphysema, while a threshold of 5% decline in one-year relative FVC should be considered in non-CPFE IPF patients.