Pediatric Pulmonology 50:1009–1016 (2015)
Spirometric Reference Values for Healthy Han Children Aged 5–15 Years in Guangzhou, Southern China Mei Jiang,1,2 Yi Gao,2 Nan-Shan Zhong,2 Wei-Qing Chen,1** Wei-Jie Guan,2 and Jin-Ping Zheng2* Summary. Background: Reliable interpretation of spirometry rests on appropriate reference values, but there are few published reference values for healthy children in China. Objective: To develop the updated spirometric normative values for healthy children aged 5–15 years in Guangzhou, southern China, and to explore the differences by comparison with published reference values. Methods: In this cross-sectional study, health questionnaire and physical examination conducted for screening healthy Han children. Spirometry was performed by welltrained technicians according to American Thoracic Society guidelines. Using Lambda-Mu-Sigma (LMS) algorithm, predicted equations for the median and lower limits of normal were derived for forced vital capacity (FVC), forced expiratory volume in one second (FEV1), peak expiratory flow (PEF), and maximal mid-expiratory flow (FEF25–75%). Predicted values were compared with other published spirometric reference equations. Results: Data were obtained from 422 healthy children (226 boys and 196 girls) aged 5–15 years. Spirometric parameters showed moderate-to-strong positive correlations with age, height, and weight in both genders, with height being the most crucial predictor. There were significant differences between spirometric values and other published reference values. Spirometric values were comparable with the data derived from the same area population in 2002, with exception of increased height and weight in the equivalent age groups. Conclusions: The present spirometric reference equations are feasible for assessment of lung function among children in southern China. Further studies for establishment of reference values for Chinese children in other regions are needed. Pediatr Pulmonol. 2015;50:1009–1016. ß 2014 Wiley Periodicals, Inc.
Key words: children; lung function; normative value; reference equations; spirometry. Funding source: Chinese Medical Association research projects, National Key Technology R&D Program of the 12th National Five-year Development Plan; Number: (No. 2012BAI05B01). 1
Department of Medical Statistics and Epidemiology, School of Public Health, Sun Yat-sen University, Guangzhou, China.
INTRODUCTION
Spirometry plays a pivotal role in the clinical evaluation and management of respiratory diseases. It is a relatively simple, non-invasive, and useful method to assess children with pulmonary disorders, and has been applied in the early detection of pediatric respiratory diseases and monitoring normal growth. The interpretation of spirometric results rests largely on the reference values,1 therefore their accuracy has important implications for individuals and health-care practice.2 It has been well documented3–6 that spirometric reference values varied across different ethnic groups. China is a large country with a vast territory and a wide variety of ethnic groups. To avoid incorrect interpretation of spirometry in a population by using predicted values derived from a different ethnicity, establishment of reference values based on specific populations in different geographical regions is warranted.2 However, there have been few published spirometry reference values for healthy children in China and currently available ß 2014 Wiley Periodicals, Inc.
2 State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Diseases, First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China.
Mei Jiang and Yi Gao contributed equally to this work. Conflict of interest: None.
Correspondence to: Jin-Ping Zheng, MD, State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Diseases, First Affiliated Hospital of Guangzhou Medical College, 151 Yanjiang Road, Guangzhou, 510120, China. E-mail: [email protected]. Correspondence to: Dr. Wei-Qing Chen, Professor of Epidemiology, Dept. of Medical Statistics and Epidemiology, School of Public Health, Sun Yat-Sen University, 74, Zhongshan Road 2, Guangzhou, 510080, Guangdong Province, China. E-mail: [email protected]. Received 25 November 2013; Revised 23 June 2014; Accepted 20 July 2014. DOI 10.1002/ppul.23099 Published online 28 August 2014 in Wiley Online Library (wileyonlinelibrary.com).
1010
Jiang et al.
reference values in southern China were derived a decade ago,7 despite that ever-improving spirometric methodology and secular trends may affect the applicability to current measurements. Additionally, methods (including statistical approaches) for determining the spirometric reference ranges can have a considerable impact on the clinical management of respiratory diseases. Modeling spirometric variables could be complicated for the variability of individual measurements around the median that may not appear uniform across the age/height range, and the skewness in data distributions has been shown previously.8 This suggests that conventional multiple linear regression analysis, the most frequently used model to generate reference equations,9,10 is not adequate to depict the intricate relationship among body size, age, and spirometric parameters. Along with the advances in measurement techniques, equipment, population dynamics and statistical methods, the adherence to obsolescent data could substantially undermine the sensitivity in detecting abnormal conditions at an early stage,11 and thus there is a dire need to keep reference values up-todate to reflect these changes8 by using proper statistical methods for Chinese children. We therefore sought to develop updated spirometric reference values for healthy Han children aged 5–15 years in Guangzhou, southern China, and to compare the results with other previously published equations. METHODS Study Population
This study was conducted between January and December 2008. Children were recruited from one each kindergarten, elementary school, and middle school which were randomly selected from Guangzhou, Southern China. Clinical evaluation was based on a combination of questionnaire and physical examination. Healthy nonsmoking Han children aged 5–15 years were included. The exclusion criteria were any history of active smoking, common cold within 4 weeks, history of chest trauma, lower respiratory tract diseases or symptoms (asthma, wheezing, persistent cough, persistent phlegm, allergic rhinitis, pulmonary tuberculosis, pneumonia, or bronchitis), or clinically relevant aberration of heart, lungs, and chest wall. Ethics committee approval for this study was obtained from the First Affiliated Hospital of Guangzhou Medical
ABBREVIATIONS: PFT Pulmonary function test ATS American Thoracic Society FEF25–75% Forced expiratory flow at 25 to 75% of expired volume LLN Lower limit of normal LMS Lambda-Mu-Sigma
Pediatric Pulmonology
University. Written informed consent was obtained from the parents or guardians of each participant before measurement of spirometry. Measurement
Parents or guardians were requested to complete a questionnaire. The data on demography, health status, and lifestyle were derived from the questionnaire, including chronic respiratory symptoms and diseases, smoking status (for parents and children entering puberty), or a history of any illness that might affect lung function. Weight and height were measured in the morning by a technician, and children wore lightweight clothing and were barefoot. Standing height was measured to the nearest 0.5 cm and weight rounded to the nearest 0.5 kg. Spirometry was performed in a seated position with computerized spirometers (Masterscreen, Jaeger Inc., Hochberg, Germany). The spirometers were calibrated once daily, prior to spirometry. All technicians were trained to follow the procedures recommended by American Thoracic Society/European Respiratory Society joint statement12 to ensure quality control. Children were instructed on the technique of the maneuvers first in small groups and the instructions were reinforced to each child individually before the tests. The children were instructed to conduct an exhaled maneuver by taking a deep inspiration followed by exhaling as fast, hard, and long as possible. End-of-test criteria13 consisted of: 1) The subject could not continue further exhalation; 2) Forced expiratory duration of 6 sec for children aged >10 yrs or 3 sec for those aged
Spirometric Reference Values for Healthy Han Children Aged 5–15 Years in Guangzhou, Southern China Mei Jiang,1,2 Yi Gao,2 Nan-Shan Zhong,2 Wei-Qing Chen,1** Wei-Jie Guan,2 and Jin-Ping Zheng2* Summary. Background: Reliable interpretation of spirometry rests on appropriate reference values, but there are few published reference values for healthy children in China. Objective: To develop the updated spirometric normative values for healthy children aged 5–15 years in Guangzhou, southern China, and to explore the differences by comparison with published reference values. Methods: In this cross-sectional study, health questionnaire and physical examination conducted for screening healthy Han children. Spirometry was performed by welltrained technicians according to American Thoracic Society guidelines. Using Lambda-Mu-Sigma (LMS) algorithm, predicted equations for the median and lower limits of normal were derived for forced vital capacity (FVC), forced expiratory volume in one second (FEV1), peak expiratory flow (PEF), and maximal mid-expiratory flow (FEF25–75%). Predicted values were compared with other published spirometric reference equations. Results: Data were obtained from 422 healthy children (226 boys and 196 girls) aged 5–15 years. Spirometric parameters showed moderate-to-strong positive correlations with age, height, and weight in both genders, with height being the most crucial predictor. There were significant differences between spirometric values and other published reference values. Spirometric values were comparable with the data derived from the same area population in 2002, with exception of increased height and weight in the equivalent age groups. Conclusions: The present spirometric reference equations are feasible for assessment of lung function among children in southern China. Further studies for establishment of reference values for Chinese children in other regions are needed. Pediatr Pulmonol. 2015;50:1009–1016. ß 2014 Wiley Periodicals, Inc.
Key words: children; lung function; normative value; reference equations; spirometry. Funding source: Chinese Medical Association research projects, National Key Technology R&D Program of the 12th National Five-year Development Plan; Number: (No. 2012BAI05B01). 1
Department of Medical Statistics and Epidemiology, School of Public Health, Sun Yat-sen University, Guangzhou, China.
INTRODUCTION
Spirometry plays a pivotal role in the clinical evaluation and management of respiratory diseases. It is a relatively simple, non-invasive, and useful method to assess children with pulmonary disorders, and has been applied in the early detection of pediatric respiratory diseases and monitoring normal growth. The interpretation of spirometric results rests largely on the reference values,1 therefore their accuracy has important implications for individuals and health-care practice.2 It has been well documented3–6 that spirometric reference values varied across different ethnic groups. China is a large country with a vast territory and a wide variety of ethnic groups. To avoid incorrect interpretation of spirometry in a population by using predicted values derived from a different ethnicity, establishment of reference values based on specific populations in different geographical regions is warranted.2 However, there have been few published spirometry reference values for healthy children in China and currently available ß 2014 Wiley Periodicals, Inc.
2 State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Diseases, First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China.
Mei Jiang and Yi Gao contributed equally to this work. Conflict of interest: None.
Correspondence to: Jin-Ping Zheng, MD, State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Diseases, First Affiliated Hospital of Guangzhou Medical College, 151 Yanjiang Road, Guangzhou, 510120, China. E-mail: [email protected]. Correspondence to: Dr. Wei-Qing Chen, Professor of Epidemiology, Dept. of Medical Statistics and Epidemiology, School of Public Health, Sun Yat-Sen University, 74, Zhongshan Road 2, Guangzhou, 510080, Guangdong Province, China. E-mail: [email protected]. Received 25 November 2013; Revised 23 June 2014; Accepted 20 July 2014. DOI 10.1002/ppul.23099 Published online 28 August 2014 in Wiley Online Library (wileyonlinelibrary.com).
1010
Jiang et al.
reference values in southern China were derived a decade ago,7 despite that ever-improving spirometric methodology and secular trends may affect the applicability to current measurements. Additionally, methods (including statistical approaches) for determining the spirometric reference ranges can have a considerable impact on the clinical management of respiratory diseases. Modeling spirometric variables could be complicated for the variability of individual measurements around the median that may not appear uniform across the age/height range, and the skewness in data distributions has been shown previously.8 This suggests that conventional multiple linear regression analysis, the most frequently used model to generate reference equations,9,10 is not adequate to depict the intricate relationship among body size, age, and spirometric parameters. Along with the advances in measurement techniques, equipment, population dynamics and statistical methods, the adherence to obsolescent data could substantially undermine the sensitivity in detecting abnormal conditions at an early stage,11 and thus there is a dire need to keep reference values up-todate to reflect these changes8 by using proper statistical methods for Chinese children. We therefore sought to develop updated spirometric reference values for healthy Han children aged 5–15 years in Guangzhou, southern China, and to compare the results with other previously published equations. METHODS Study Population
This study was conducted between January and December 2008. Children were recruited from one each kindergarten, elementary school, and middle school which were randomly selected from Guangzhou, Southern China. Clinical evaluation was based on a combination of questionnaire and physical examination. Healthy nonsmoking Han children aged 5–15 years were included. The exclusion criteria were any history of active smoking, common cold within 4 weeks, history of chest trauma, lower respiratory tract diseases or symptoms (asthma, wheezing, persistent cough, persistent phlegm, allergic rhinitis, pulmonary tuberculosis, pneumonia, or bronchitis), or clinically relevant aberration of heart, lungs, and chest wall. Ethics committee approval for this study was obtained from the First Affiliated Hospital of Guangzhou Medical
ABBREVIATIONS: PFT Pulmonary function test ATS American Thoracic Society FEF25–75% Forced expiratory flow at 25 to 75% of expired volume LLN Lower limit of normal LMS Lambda-Mu-Sigma
Pediatric Pulmonology
University. Written informed consent was obtained from the parents or guardians of each participant before measurement of spirometry. Measurement
Parents or guardians were requested to complete a questionnaire. The data on demography, health status, and lifestyle were derived from the questionnaire, including chronic respiratory symptoms and diseases, smoking status (for parents and children entering puberty), or a history of any illness that might affect lung function. Weight and height were measured in the morning by a technician, and children wore lightweight clothing and were barefoot. Standing height was measured to the nearest 0.5 cm and weight rounded to the nearest 0.5 kg. Spirometry was performed in a seated position with computerized spirometers (Masterscreen, Jaeger Inc., Hochberg, Germany). The spirometers were calibrated once daily, prior to spirometry. All technicians were trained to follow the procedures recommended by American Thoracic Society/European Respiratory Society joint statement12 to ensure quality control. Children were instructed on the technique of the maneuvers first in small groups and the instructions were reinforced to each child individually before the tests. The children were instructed to conduct an exhaled maneuver by taking a deep inspiration followed by exhaling as fast, hard, and long as possible. End-of-test criteria13 consisted of: 1) The subject could not continue further exhalation; 2) Forced expiratory duration of 6 sec for children aged >10 yrs or 3 sec for those aged
