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Ra, Park, Hong, Hong, Shim, Lim, Lee, Koh, Kim, Kim, Kim, and Oh: Clinical Usefulness and the Accuracy of Korean Reference Equation for Diffusing Capacity
Original Article
Tuberculosis and Respiratory Diseases

Tuberculosis and Respiratory Diseases 2008; 64(2): 80-86.

Published online: 29 February 2008

DOI: https://doi.org/10.4046/trd.2008.64.2.80

Clinical Usefulness and the Accuracy of Korean Reference Equation for Diffusing Capacity

Seung Won Ra, M.D.1, Tai Sun Park, M.D.1, Yoonki Hong, M.D.1, Sang-Bum Hong, M.D.1, Tae Sun Shim, M.D.1, Chae-Man Lim, M.D.1, Sang-Do Lee, M.D.1, 2, Younsuck Koh, M.D.1, Woo Sung Kim, M.D.1, Dong-Soon Kim, M.D.1, Won Dong Kim, M.D.1, Yeon-Mok Oh, M.D.1, 2

1Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.

2Clinical 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 2-dong, Songpa-gu, Seoul 138-736, Korea. Phone: 82-2-3010-3136, Fax: 82-2-3010-6968, ymoh55@amc.seoul.kr

Received 5 January 2008       Accepted 21 January 2008

Copyright © 2008 The Korean Academy of Tuberculosis and Respiratory Diseases

Abstract

Background

Park et al. developed the Korean reference equation for the measurement of diffusing capacity in 1985. However, the equation has not been widely used in Korea and foreign reference equations have been popularly used. We intended to compare the clinical usefulness and the accuracy of the the Korean reference equation (Park's equation) with that of the foreign equation (Burrows' equation) that is commonly used in Korea.

Methods

1. Evaluation of clinical usefulness; Among 1,584 patients who underwent diffusing capacity (DLCO) at the Asan Medical Center from July to December 2006, group A subjects included 276 patients who had different interpretations of DLCO in trials employing Burrows' equation and Park's equation. Clinical assessment was decided by consensus of two respiratory physicians. In order to evaluate the clinical usefulness of Burrows' equation and Park's equation, agreement of clinical assessment and DLCO interpretation were measured. 2. Evaluation of accuracy; Group B subjects were 81 patients with interstitial lung disease (ILD) and 39 normal subjects. The 81 ILD patients were diagnosed following a surgical lung biopsy. The accuracy of diagnosing ILD as well as sensitivity and specificity were evaluated according to the use of the reference equations (Burrows' equation and Park's equation) for DLCO.

Results

Agreement between clinical assessment and interpretation of DLCO was 22% for the use of Burrows' equation and 78% for the use of Park's equation. The sensitivity and specificity of the Burrows' equation for diagnosing ILD were 64.2% and 100%. The sensitivity and specificity of the Park's equation for diagnosing ILD were 90.1% and 100%. The sensitivity of the Park's equation for diagnosing ILD was significantly higher than that of Burrows' equation (p<0.001).

Conclusion

The Korean reference equation (Park's equation) was more clinically useful and had higher sensitivity for diagnosing ILD than the foreign reference equation (Burrows' equation).

Keywords: Diffusing capacity, Reference equations, Clinical usefulness, Accuracy

Figures and Tables

Figure 1
Extraction of study subject group A.
*Subjects those of less than 20 years old (743 subjects), non-Korean ethnicity (8 subjects), repeated cases (1,083 subjects), not doing diffusing capacity (7,548 subjects), and not doing lung volumes (507 subjects) were excluded.
†Applying the Burrows' and the Park's equations using the lower limits of normal (LLN) by 95% confidence interval method to interpret PFT and to examine agreement between two equations.
‡Change of PFT interpretation by the Burrows' equation to the Park's.
N → N: normal by the Burrows' equation → normal by the Park's equation; D → D: decrease by the Burrows' equation → decrease by the Park's equation; N → D: normal by the Burrows' equation → decrease by the Park's equation; D → N: decrease by the Burrows' equation → normal by the Park's equation.
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Table 1
Baseline characteristics of subject group A
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DLCO: diffusing lung capacity of carbon monoxide in lung.

*Mean±standard deviation.

Table 2
Clinical assessment of the subject group A
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ILD: interstitial lung disease, HTN: hypertension.

*others include lymphangitic lung metastasis (5 subjects), pulmonary tuberculosis (3), pneumoconiosis (2), lymphoma (1), miliary tuberculosis (1).

Table 3
The agreement between clinical assessment and interpretation by two reference equations (n=276)
trd-64-80-i003

*normal by the Burrows' equation → decrease by the Park's equation, †decrease by the Burrows' equation → normal by the Park's equation, The agreement between clinical assessment and interpretation by the Burrows' equation and by the Park's equation: 60 (22%) vs 214 (78%), p<0.01 by the Chi-square test.

Table 4
The difference in change of interpretation based on gender and BMI (body mass index)
trd-64-80-i004

*normal by the Burrows' equation → decrease by the Park's equation, †decrease by the Burrows' equation → normal by the Park's equation, ‡All of 8 subjects were obese women and the clinical assessment of 7 subjects was 'decrease'.

Table 5
Baseline characteristics of subject group B
trd-64-80-i005

DLCO: diffusing lung capacity of carbon monoxide in lung; ILD: interstitial lung disease.

Table 6
The accuracies of diffusing capacity when applying the Burrows' and the Park's equation to diagnose ILD
trd-64-80-i006

ILD: interstitial lung disease.

*p<0.001 (McNemar test).

Lower limit of normal was determined by 95% confidence interval method.

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