2007 - Reference values of diffusing capacity of non-smoking Chinese in Hong Kong
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.