Adult Lung Function Study

Arthur Chun-Wing Lau, MBBS, MRCP, FCCP, Mary Sau-Man Ip, MD, FRCP, FCCP, Christopher Kei-Wai Lai, DM, FRCP, Kah-Lin Choo, FRCP, FCCP, Kam-Shing Tang, MBBS, MRCP, Loretta Yin-Chun Yam, MBBS, FRCP, FCCP, and Moira Chan-Yeung, MBBS, FRCP, FCCP

CHEST January 2008 vol. 133 no. 1 42-48

*From the Department of Intensive Care (Dr. Lau), Division of Respiratory and Critical Care Medicine (Dr. Yam), Department of Medicine, Pamela Youde Nethersole Eastern Hospital; University Department of Medicine (Drs. Ip and Chan-Yeung), The University of Hong Kong, Queen Mary Hospital; The Chinese University of Hong Kong (Dr. Lai); Department of Medicine (Dr. Choo), North District Hospital, Hong Kong; and Intensive Care Unit (Dr. Tang), Tuen Mun Hospital, Hong Kong, SAR, China.

Abstract

Purpose

To estimate the prevalence of undiagnosed airflow obstruction (AFO) in Hong Kong smokers with no previous diagnosis of respiratory disease, and to assess its variability when applying different prediction equations and diagnostic criteria.

Methods

 A multicenter, population-based, cross-sectional prevalence study was performed in smokers aged 20 to 80 years. Three different criteria (fixed 70% [Global Initiative for Chronic Obstructive Lung Disease and British Thoracic Society], fixed 75%, and European Respiratory Society [ERS]) were applied to define a lower limit of normal (LLN) of the FEV1/FVC ratio to compare with the Hong Kong Chinese reference equation (criterion 1), which had used a distribution-free method to obtain the lower fifth percentile of FEV1/FVC ratio as the LLN.

Results

In 525 male patients, using criterion 1 (local internal prediction equation) and defining AFO as FEV1/FVC less than LLN, the overall prevalence of AFO was 13.7%: 8.3% in age ≥ 20 to 40 years, 14.0% in age ≥ 40 to 60 years, and 17.8% in age ≥ 60 to 80 years. When the local internal prediction equation was used as the comparison reference, the fixed-ratio methods tended to miss AFO in younger age groups and overdiagnose AFO in old age, while the ERS criteria, which uses an almost lower fifth percentile-equivalent method, showed less of such a trend but still only showed moderate agreement with criterion 1.

Conclusions

 Undiagnosed AFO was prevalent in Hong Kong smokers. Estimated prevalence rates were highly affected by the criteria used to define AFO. The predicted lower fifth percentile values calculated from a local reference equation as the LLN of FEV1/FVC ratio should be used for the diagnosis of AFO.

Mary Sau-man Ip, MD, FCCP, Fanny Wai-san Ko, MBChB, FCCP, Arthur Chun-wing Lau, MBBS, FCCP, Wai-cho Yu, MBBS, FCCP, Kam-shing Tang, MBBS, Kahlin Choo, BMBS, FCCP, Moira Mo-wah Chan-Yeung, MBBS, FCCP, and on Behalf of the Hong Kong Thoracic Society and American College of Chest Physicians (Hong Kong and Macau Chapter)

CHEST February 2006 vol. 129 no. 2 384-392

*From the Department of Medicine (Drs. Ip and Chan-Yeung), The University of Hong Kong, Queen Mary Hospital; Department of Medicine and Therapeutics (Dr. Ko), The Chinese University of Hong Kong, Prince of Wales Hospital; Department of Medicine (Dr. Lau), Pamela Youde Nethersole Eastern Hospital; Department of Medicine (Dr. Yu), Princess Margaret Hospital; Department of Medicine (Dr. Tang), Tuen Mun Hospital; and Department of Medicine (Dr. Choo), Northern District Hospital, Hong Kong SAR, China.

Abstract

Study objectives

The accuracy of reference values of lung function is important for assessment of severity and functional impairment of respiratory diseases. The aim of the study was to establish updated prediction formulae of spirometric parameters for Hong Kong Chinese and to compare the reference values with those derived from other studies in white and Chinese subjects.

Design

Cross-sectional multicenter study.

Setting

Lung function laboratories of eight regional hospitals in Hong Kong.

Participants

Subjects were recruited by random-digit dialing. One thousand one hundred seventy-six subjects who fulfilled recruitment criteria underwent spirometry.

Measurements

Spirometry was performed according to American Thoracic Society recommendations, and the technique was standardized among the eight participating lung function laboratories.

Results

Evaluable data of 1,089 (494 men and 595 women) healthy nonsmokers aged 18 to 80 years were analyzed. Age and height were found to be the major determinants of FEV1 and FVC, with a linear decline of height-adjusted values with age in both sexes. Spirometric values of this population have increased compared to Chinese populations of similar sex, age, and height two decades ago. Reference values derived from white populations were higher than our values by 5 to 19%, and the degree of overestimation varied with age, sex, and lung function parameter. We also demonstrated that the blanket application of correction factors for Asian populations may not be appropriate. In this study cohort, the distribution-free estimation of age-related centiles was more appropriate for the determination of lower limits of normal.

Conclusions

Our findings underscore the need to use reference values based on updated data derived from local populations or those matched for ethnicity and other sociodemographic characteristics.

Ip MS, Lam WK, Lai AY, Ko FW, Lau AC, Ling SO, Chan JW, Chan-Yeung MM; Hong Kong Thoracic Society. Respirology. 2007 Jul;12(4):599-606.

Department of Medicine, University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong, China. msmip@hkucc.hku.hk

BACKGROUND AND OBJECTIVE: This study was conducted to define normal reference values and lower limits of normal (LLN) for single-breath carbon monoxide diffusing capacity (DLco) and DLco per unit of alveolar volume (Kco) for Chinese adults in Hong Kong.

METHODS: Healthy non-smoking men and women aged 18-80 years were recruited by random digit dialing. DLco and Kco were measured according to American Thoracic Society standards. Reference equations were obtained by multiple linear regression; LLN were derived by distribution-free method for estimation of age-related centiles.

RESULTS: Tests from 568 subjects (259 men, 309 women) were analysed. DLco declined with age in both genders, and increased with height and the interaction term of height and age in men and women, respectively. Considering Hb values did not improve the reference equations. Kco declined with age and increased with weight in both genders, while height and its interaction term with age were additional determinants in women. The reference DLco was lower than some Caucasian values, and was only explained partially by a smaller body size and alveolar volume in Chinese. The distribution-free method yielded better overall approximation to the fifth percentile compared with the traditional method of determining LLN.

CONCLUSIONS: The equations for reference values and LLN of diffusing capacity derived in this study are of clinical relevance to Chinese subjects.