Back to Journals » International Journal of Chronic Obstructive Pulmonary Disease » Volume 13

Comparison of the fixed ratio and the Z-score of FEV1/FVC in the elderly population: a long-term mortality analysis from the Third National Health and Nutritional Examination Survey

Authors Oh DK, Baek S, Lee SW, Lee JS, Lee SD, Oh YM

Received 5 August 2017

Accepted for publication 28 December 2017

Published 14 March 2018 Volume 2018:13 Pages 903—915

DOI https://doi.org/10.2147/COPD.S148421

Checked for plagiarism Yes

Review by Single-blind

Peer reviewers approved by Dr Amy Norman

Peer reviewer comments 2

Editor who approved publication: Dr Richard Russell


Dong Kyu Oh,1 Seunghee Baek,2 Sei Won Lee,1 Jae Seung Lee,1 Sang-Do Lee,1 Yeon-Mok Oh1

1Department of Pulmonary and Critical Care Medicine, Clinical Research Center for Chronic Obstructive Airway Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea; 2Department of Clinical Epidemiology and Biostatistics, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea

Background and objective: Despite the ongoing intense debate on the definition of airflow limitation by spirometry in the elderly population, there have only been few studies comparing the fixed ratio and the Z-score of forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) in terms of long-term mortalities. In this study, we aimed to identify the proper method for accurately defining the airflow limitation in terms of long-term mortality prediction in the elderly population.
Methods: Data were collected from the Third National Health and Nutrition Examination Survey in the US. Non-Hispanic Caucasians aged 65–80 years were included. The receiver operating characteristic (ROC) curves of both methods were plotted and compared for 10-year all-cause, respiratory, and COPD mortalities.
Results: Of 1,331 subjects, the mean age was 71.7 years and 805 (60.5%) were males. For the 10-year all-cause mortality, the area under the curve (AUC) of the fixed ratio was significantly greater than that of the Z-score of FEV1/FVC, but both showed poor prediction performance (0.633 vs 0.616, p<0.001). For the 10-year respiratory and COPD mortalities, both the fixed ratio and the Z-score of FEV1/FVC showed comparable prediction performance with greater AUCs (0.784 vs 0.778, p=0.160, and 0.896 vs 0.896, p=0.971, respectively). Interestingly, the conventional cutoff of 0.7 in the fixed ratio was consistently higher than the optimal for the 10-year all-cause, respiratory, and COPD mortalities (0.70 vs 0.69, 0.62, and 0.61, respectively), whereas that of -1.64 in the Z-score of FEV1/FVC was consistently lower than the optimal cutoff (-1.64 vs -1.31, -1.47, and -1.41, respectively).
Conclusion: In the elderly population, both the fixed ratio and the Z-score of FEV1/FVC showed comparable prediction performance for the 10-year respiratory and COPD mortalities. However, the conventional cutoff of neither 0.70 in the fixed ratio nor -1.64 in the Z-score of FEV1/FVC was optimal for predicting the long-term mortalities.

Keywords: airway obstruction, chronic obstructive pulmonary disease, mortality, pulmonary disease, ROC curve, spirometry

Creative Commons License This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution - Non Commercial (unported, v3.0) License. By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms.

Download Article [PDF]  View Full Text [HTML][Machine readable]