Prediction of lung emphysema in COPD by spirometry and clinical symptoms: results from COSYCONET

Christina Kellerer,Rudolf A Jörres,Johanna Lutter,Henrik Watz,Antonius Schneider,Bertram Jobst,Jürgen Behr,Jürgen Biederer,Robert Bals,Peter Alter,Alexander Hapfelmeier,Claus F Vogelmeier,Diego Kauffmann-Guerrero,Hans-Ulrich Kauczor,Franziska C Trudzinski,Kathrin Kahnert,Helgo Magnussen,Tobias Welte

doi:10.1186/s12931-021-01837-2

Abstract

BackgroundLung emphysema is an important phenotype of chronic obstructive pulmonary disease (COPD), and CT scanning is strongly recommended to establish the diagnosis. This study aimed to identify criteria by which physicians with limited technical resources can improve the diagnosis of emphysema.MethodsWe studied 436 COPD patients with prospective CT scans from the COSYCONET cohort. All items of the COPD Assessment Test (CAT) and the St George’s Respiratory Questionnaire (SGRQ), the modified Medical Research Council (mMRC) scale, as well as data from spirometry and CO diffusing capacity, were used to construct binary decision trees. The importance of parameters was checked by the Random Forest and AdaBoost machine learning algorithms.ResultsWhen relying on questionnaires only, items CAT 1 & 7 and SGRQ 8 & 12 sub-item 3 were most important for the emphysema- versus airway-dominated phenotype, and among the spirometric measures FEV1/FVC. The combination of CAT item 1 (≤ 2) with mMRC (> 1) and FEV1/FVC, could raise the odds for emphysema by factor 7.7. About 50% of patients showed combinations of values that did not markedly alter the likelihood for the phenotypes, and these could be easily identified in the trees. Inclusion of CO diffusing capacity revealed the transfer coefficient as dominant measure. The results of machine learning were consistent with those of the single trees.ConclusionsSelected items (cough, sleep, breathlessness, chest condition, slow walking) from comprehensive COPD questionnaires in combination with FEV1/FVC could raise or lower the likelihood for lung emphysema in patients with COPD. The simple, parsimonious approach proposed by us might help if diagnostic resources regarding respiratory diseases are limited.Trial registration ClinicalTrials.gov, Identifier: NCT01245933, registered 18 November 2010, https://clinicaltrials.gov/ct2/show/record/NCT01245933.

Highlights

Lung emphysema is an important phenotype of chronic obstructive pulmonary disease (COPD), and CT scanning is strongly recommended to establish the diagnosis
To compare the methods we show the variables selected by these procedures in the rank order of importance according to the criterion of the mean decrease in accuracy (Random Forest) and the importance measure defined in the AdaBoost procedure, whereby the overall classification error refers to tenfold cross-validation in the case of AdaBoost and CHAID
Study cohort Of the 1427 patients participating in visit 4, 436 patients were eligible for analysis by having data on the presence of emphysema from the CT scoring and being categorized as COPD grades 1 to 4 (Table 1)

Summary

Introduction

Lung emphysema is an important phenotype of chronic obstructive pulmonary disease (COPD), and CT scanning is strongly recommended to establish the diagnosis. Lung emphysema is an important phenotype of COPD, and the differentiation between emphysema- and Kellerer et al Respir Res (2021) 22:242 airway-phenotypes is increasingly relevant for the management of the disease. The differentiation between bronchitis and emphysema is important as emphysema shows functional characteristics different from those of chronic obstructive bronchitis [6,7,8], and patients with emphysema have partially different therapeutic options, such as lung volume reduction in case of severe hyperinflation [9,10,11], that are not relevant for predominant obstructive bronchitis. Emphysema is associated with increased mortality risk and incidence of lung cancer [13, 14]

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