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Ra, Oh, Hong, Shim, Lim, Koh, Lee, Kim, Kim, Kim, and Oh: Effect of the Changing the Lower Limits of Normal and the Interpretative Strategies for Lung Function Tests
Original Article
Tuberculosis and Respiratory Diseases

Tuberculosis and Respiratory Diseases 2006; 61(2): 129-136.

Published online: 31 August 2006

DOI: https://doi.org/10.4046/trd.2006.61.2.129

Effect of the Changing the Lower Limits of Normal and the Interpretative Strategies for Lung Function Tests

Seung Won Ra, M.D., Ji Seon Oh, M.D., Sang-Bum Hong, M.D., Tae Sun Shim, M.D., Chae-Man Lim, M.D., Youn Suck Koh, M.D., Sang Do Lee, M.D., Woo Sung Kim, M.D., Dong-Soon Kim, M.D., Won Dong Kim, M.D., Yeon-Mok Oh, M.D.

Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine and the Clinical Research Center for Chronic Obstructive Airway Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.

Address for correspondence: Yeon-Mok Oh, M.D. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine and Clinical Research Center for Chronic Obstructive Airway Diseases, Asan Medical Center, University of Ulsan College of Medicine 388-1 Pungnap-2dong, Songpa-gu, Seoul, Zip #138-736, Korea. Phone: 02-3010-3136, FAX: 02-3010-6968, ymoh55@amc.seoul.kr

Received 27 June 2006       Accepted 18 July 2006

Copyright © 2006 The Korean Academy of Tuberculosis and Respiratory Diseases

Abstract

Background

To interpret lung function tests, it is necessary to determine the lower limits of normal (LLN) and to derive a consensus on the interpretative algorithm. '0.7 of LLN for the FEV1/FVC' was suggested by the COPD International Guideline (GOLD) for defining obstructive disease. A consensus on a new interpretative algorithm was recently achieved by ATS/ERS in 2005. We evaluated the accuracy of '0.7 of LLN for the FEV1/FVC' for diagnosing obstructive diseases, and we also determined the effect of the new algorithm on diagnosing ventilatory defects.

Methods

We obtained the age, gender, height, weight, FEV1, FVC, and FEV1/FVC from 7362 subjects who underwent spirometry in 2005 at the Asan Medical Center, Korea. For diagnosing obstructive diseases, the accuracy of '0.7 of LLN for the FEV1/FVC' was evaluated in reference to the 5th percentile of the LLN. By applying the new algorithm, we determined how many more subjects should have lung volumes testing performed. Evaluation of 1611 patients who had lung volumes testing performed as well as spirometry during the period showed how many more subjects were diagnosed with obstructive diseases according to the new algorithm.

Results

1) The sensitivity of '0.7 of LLN for the FEV1/FVC' for diagnosing obstructive diseases increased according to age, but the specificity was decreased according to age; the positive predictive value decreased, but the negative predictive value increased. 2) By applying the new algorithm, 34.5% (2540/7362) more subjects should have lung volumes testing performed. 3) By applying the new algorithm, 13% (205/1611) more subjects were diagnosed with obstructive diseases; these subjects corresponded to 30% (205/681) of the subjects who had been diagnosed with restrictive diseases by the old interpretative algorithm.

Conclusion

The sensitivity and specificity of '0.7 of LLN for the FEV1/FVC' for diagnosing obstructive diseases changes according to age. By applying the new interpretative algorithm, it was shown that more subjects should have lung volumes testing performed, and there was a higher probability of being diagnosed with obstructive diseases.

Keywords: Lung function test, Interpretation, Lower limits of normal, Algorithm

Figures and Tables

Figure 1
Algorithms for the interpretation of lung function tests
The left algorithm (A) was suggested by American Thoracic Society(ATS) in 1991; the right (B) by American Thoracic Society/European Respiratory Society(ATS/ERS) in 2005. FEV1, forced expiratory volume in one second; FVC, forced vital capacity; LLN, lower limits of normal; TLC, total lung capacity
trd-61-129-g001
Figure 2
Sensitivity and specificity of 'FEV1/FVC < 0.7' diagnosing obstructive diseases.
Spirometry was performed for 7362 patients from July 1 to November 30, 2005 in the Asan Medical Center. 'FEV1/FVC < 5th percentile' was used as the gold standard to define obstructive diseases.
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Figure 3
Positive predictive value(PPV) and negative predictive value(NPV) of 'FEV1/FVC < 0.7' diagnosing obstructive diseases.
Spirometry was performed for 7362 patients from July 1 to November 30, 2005 in the Asan Medical Center. 'FEV1/FVC < 5th percentile' was used as the gold standard to define obstructive diseases.
trd-61-129-g003
Figure 4
Application of the new ATS/ERS algorithm for the interpretation of lung function tests requires that 34.5% of subjects should perform additional lung volumes testing to obtain TLC. The numbers in the algorithm represent numbers of subjects in each flow; the percentages in parentheses represent percentage of subjects to all subjects (n=7362). For the 7362 subjects, spirometry was performed from July 1 to November 30, 2005 in the Asan Medical Center.
FEV1, forced expiratory volume in one second; FVC, forced vital capacity; LLN, lower limits of normal; TLC, total lung capacity; ATS/ERS, American Thoracic Society/European Respiratory Society
trd-61-129-g004
Figure 5
Application of the new ATS/ERS algorithm for the interpretation of lung function tests revealed that additional 205 subjects were diagnosed as obstructive diseases.
The numbers in the algorithm represent numbers of subjects in each flow; the percentages in parentheses represent percentage of subjects to all subjects (n=1611). For the 1611 subjects, both spirometry and lung volumes testing were performed on the same date from July 1 to November 30, 2005 in the Asan Medical Center.
FEV1, forced expiratory volume in one second; FVC, forced vital capacity; LLN, lower limits of normal; TLC, total lung capacity; ATS/ERS, American Thoracic Society/European Respiratory Society.
trd-61-129-g005
Table 1
Characteristics of the subjects (group A)
trd-61-129-i001

*Mean ± standard deviation

†% Predicted value

Table 2
Characteristics of the subjects (group B)
trd-61-129-i002

*Mean ± standard deviation

†% Predicted value

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