Appropriate scaling approach for evaluating peak VO2 development in Southern Chinese 8 to 16 years old.

OBJECTIVE: To investigate scaling approaches for evaluating the development of peak VO2 and improving the identification of low cardiopulmonary fitness in Southern Chinese children and adolescents. METHODS: Nine hundred and twenty Chinese children and adolescents (8 to 16 years) underwent graded cardiopulmonary exercise test on a treadmill until volitional exhaustion. Peak VO2 was corrected for the effects of body mass by ratio or allometric scaling. Z score equations for predicting peak VO2 were developed. Correlations between scaled peak VO2, z scores, body size and age were tested to examine the effectiveness of the approach. RESULTS: Eight hundred and fifty-two participants (48% male) were included in the analyses. Absolute peak VO2 significantly increased with age in both sexes (both P<0.05), while ratio-scaled peak VO2 increased only in males (P<0.05). Allometrically scaled peak VO2 increased from 11 years in both sexes, plateauing by 12 years in girls and continuing to rise until 15 years in boys. Allometically scaled peak VO2 was not correlated with body mass, but remained correlated with height and age in all but the older girls. Peak VO2 z score was not correlated with body mass, height or age. CONCLUSIONS: Absolute and allometric scaled peak VO2 values are provided for Hong Kong Chinese children and adolescents by age and sex. Peak VO2 z scores improve the evaluation of cardiopulmonary fitness, allowing comparisons across ages and sex and will likely provide a better metric for tracking change over time in children and adolescents, regardless of body size and age.

Establishing International Blood Pressure References Among Nonoverweight Children and Adolescents Aged 6 to 17 Years.

BACKGROUND: Several distributions of country-specific blood pressure (BP) percentiles by sex, age, and height for children and adolescents have been established worldwide. However, there are no globally unified BP references for defining elevated BP in children and adolescents, which limits international comparisons of the prevalence of pediatric elevated BP. We aimed to establish international BP references for children and adolescents by using 7 nationally representative data sets (China, India, Iran, Korea, Poland, Tunisia, and the United States). METHODS AND RESULTS: Data on BP for 52 636 nonoverweight children and adolescents aged 6 to 19 years were obtained from 7 large nationally representative cross-sectional surveys in China, India, Iran, Korea, Poland, Tunisia, and the United States. BP values were obtained with certified mercury sphygmomanometers in all 7 countries by using standard procedures for BP measurement. Smoothed BP percentiles (50th, 90th, 95th, and 99th) by age and height were estimated by using the Generalized Additive Model for Location Scale and Shape model. BP values were similar between males and females until the age of 13 years and were higher in males than females thereafter. In comparison with the BP levels of the 90th and 95th percentiles of the US Fourth Report at median height, systolic BP of the corresponding percentiles of these international references was lower, whereas diastolic BP was similar. CONCLUSIONS: These international BP references will be a useful tool for international comparison of the prevalence of elevated BP in children and adolescents and may help to identify hypertensive youths in diverse populations.

Oscillometric 24-h ambulatory blood pressure reference values in Hong Kong Chinese children and adolescents.

OBJECTIVES: We aimed to establish community-based normal reference values of 24-h ambulatory blood pressure monitoring (ABPM) for Chinese children and adolescents. Furthermore, we investigated how excluding overweight children affects BP percentiles and compared them with German references. METHODS: In this territory-wide cross-sectional prospective cohort study, 1445 Hong Kong Chinese children and adolescents aged 8-17 years with body height between 119 and 185 cm were recruited. Their ABPM assessment was performed using validated arm oscillometric recorders (A&D TM-2430) and complied with American Heart Association's recommendations. The reference tables were constructed using the LMS method to normalize skewed distribution of ABP data to sex and age or height. RESULTS: The ambulatory BP was higher among boys and the difference between boys and girls progressively widened with age. An increasing trend in daytime and night-time SBP and DBP with age and height was observed in both sexes. The age-specific and sex-specific 95th percentiles from nonoverweight children (n=1147; 79%) were lower than the whole cohort by up to 2.5 and 1 mmHg for SBP and DBP, respectively. In comparison, our overall and nonoverweight reference standards were generally higher than corresponding German references. CONCLUSION: The study provides ambulatory BP standards for Chinese children, with sex-related age-specific and height-specific percentiles. Further longitudinal studies are required for investigating its clinical utility in Chinese.

A pilot randomized study to assess immunogenicity, reactogenicity, safety and tolerability of two human papillomavirus vaccines administered intramuscularly and intradermally to females aged 18-26 years.

Intradermal administration of human papillomavirus (HPV) vaccines could be dose-sparing and cost-saving. This pilot randomized study assessed Cervarix(®) and Gardasil(®) administered either intramuscularly or intradermally, in different doses (full-dose or reduced to 20%) by different methods (needle and syringe or PharmaJet needle-free jet injection device). Following an initial reactogenicity study of 10 male subjects, sexually naïve women aged 18-26 years were randomized to the eight study groups to receive vaccine at 0, 2 and 6 months. 42 female subjects were enrolled and complete data were available for 40 subjects. Intradermal administration of either vaccine raised no safety concerns but was more reactogenic than intramuscular administration, although still tolerable. All subjects demonstrated a seroconversion (titre≥1:320) by Day 95. Further evaluation of intradermal HPV vaccination and its potential for cost reduction in resource poor settings is warranted.

Resting heart rate in children and adolescents: association with blood pressure, exercise and obesity.

OBJECTIVE: Resting heart rate (RHR) is increasingly recognised as a prognostic marker for long term cardiovascular outcomes in adults. This study assessed associations of RHR with blood pressure (BP), anthropometry and exercise in a large representative sample of Hong Kong children. STUDY DESIGN, SETTING AND SUBJECTS: A territory-wide growth survey carried out in 2005-2006 included students sampled from each of Hong Kong's 18 districts. RHR and BP were measured by validated oscillometric BP devices and anthropometric data and exercise frequency were recorded. Multiple linear regressions were used to test associations among RHR and BP, anthropometry and exercise frequency. RESULTS: Data on 14 842 children aged 6-18 years were available. Multiple linear regression analyses showed that RHR was positively associated with BP, and negatively associated with age and exercise frequency (p<0.001). RHR was more positively linked to waist circumference among the anthropometric measurements, and positive independent association was only identified in boys (p<0.001). CONCLUSIONS: Elevated RHR is independently associated with elevated BP in children, whereas increased structured exercise is related to lower RHR.

Self-reported body weight and height: an assessment tool for identifying children with overweight/obesity status and cardiometabolic risk factors clustering.

Body mass index (BMI) is commonly used for assessing body fat. Self-reported body weight and height derived BMI (SRDBMI) is a simple, low cost and non-invasive assessment tool and it may be a useful self-reported assessment tool to monitor the prevalence of overweight/obesity in community settings and for epidemiological research. We assessed the agreement of BW and BH between assessor measured and child self-reported values and evaluated the diagnostic ability of SRDBMI to identify children with overweight/obesity status and cardiometabolic risk factors (CMRFs) clustering. A cross-sectional study was conducted in school settings using a cluster sampling method. A total of 1,614 children aged 6-18 years were included in the analysis. Children were given a questionnaire to complete at home prior to the anthropometric measurements and blood taking at the schools. There was almost perfect agreement on BW, BH and BMI between self-reported and measured values [intraclass correlation coefficients ranged from 0.93 (95% CI: 0.93-0.94) to 0.99 (95% CI: 0.98-0.99)]. About half of the children reported their BW and BH absolute values within 1 kg and 2 cm of measured values, respectively. The SRDBMI demonstrated good diagnostic ability for identifying children with overweight/obesity status (sensitivity, specificity, positive and negative predictive values ranged from 0.83 to 0.98) and CMRFs clustering (AUC-ROCs values of BMI between measured and self-reported values were close ranging from 0.85 to 0.89). Self-reported BW and BH demonstrated almost perfect agreement with measured values and could substantially identify children with overweight/obesity status and CMRFs clustering.

Follow up of aerobic capacity in children affected by severe acute respiratory syndrome.

BACKGROUND AND OBJECTIVE: The aim of this study was to investigate the aerobic capacity of children 3 years after they were diagnosed with severe acute respiratory syndrome (SARS). METHODS: Twenty-seven patients who completed both pulmonary function and maximal aerobic capacity tests at 6 and 15 months after the acute illness were invited to return for reassessment. RESULTS: Twenty-one patients (median age 18.2 years, interquartile range (IQR) 16.5-19.7) completed all investigations at 36 months. Pulmonary function was normal in all patients. Maximal aerobic capacity, peak oxygen pulse (peak VO(2) ) and ventilatory anaerobic threshold showed significant improvements compared with values measured at 6 months in both boys and girls. In girls, ventilatory efficiency (ventilatory equivalents for oxygen and carbon dioxide) and perfusion of the lungs (end-tidal partial carbon dioxide pressure) had not increased further compared with the values measured at 15 months. Although peak VO(2) improved further at 36 months in patients with or without persistent radiological abnormalities, the values were 68% (IQR 50-84) and 74% (IQR 60-99), respectively, of those for normal control subjects. CONCLUSIONS: There were improvements in aerobic capacity at 36 months in children affected by SARS; however, the measured values remained suboptimal.

Prevalence and risk factors for hypertension in Hong Kong Chinese adolescents: waist circumference predicts hypertension, exercise decreases risk.

PURPOSE: To determine the prevalence, risk factors for and patterns of hypertension in Chinese adolescents based on a territory-wide school based screening programme in Hong Kong. METHODS: Cross-sectional anthropometric and oscillometric blood pressure (BP) measurements and lifestyle information were obtained as part of a growth survey of students from randomly selected secondary schools in Hong Kong. Those with blood pressure ≥ 95th centile were screened a second or third time. Hypertension is defined as elevated blood pressure on three separate occasions. The independent effects of age, sex, body mass index, high waist circumference (≥ 85th centile), sleep duration, family history of hypertension and frequency of exercise on hypertension were explored by multivariate analysis. RESULTS: Among the 6193 students screened, the prevalence of elevated blood pressure on the first, second and third screens was 9.54%, 2.77% and 1.44% respectively. Hypertension was more likely to be systolic. High waist circumference (≥ 85th centile) was independently associated with a higher risk of hypertension (adjusted OR 2.4), while exercising twice or more per week was protective (adjusted OR 0.28). CONCLUSIONS: The prevalence of hypertension in Hong Kong Chinese adolescents is 1.44%. The current study shows high waist circumference is a predictor of hypertension in adolescents, while increased physical activity is a protective factor. Incorporating waist circumference into screening protocols may increase the sensitivity of cardiovascular risk stratification. Healthcare providers should be strong advocates helping to prevent obesity and promote physical activity in adolescents and children.

Measurement of pubertal status with a Chinese self-report Pubertal Development Scale.

This cross sectional study of 290 Chinese children aged 8-18 years, evaluated a Chinese version of the self-reported Pubertal Development Scale (PDS) against both raters' and self-reported Tanner assessment of pubertal status. Children completed both the self-reported PDS and self-reported Tanner pubertal questionnaire prior to physical examination through visual depiction by a same gender rater. Puberty Category Scores (PCS) which were derived from the PDS, was used to categorize children into one of five pubertal development stages. Tanner derived composite stage (TDCS) which was derived from the Tanner pubertal questionnaires, was used to compare with PCS to obtain the inter-rater agreement. Moderately high agreements were found between raters' TDCS and PCS in girls [weighted kappa (WK) 0.57 (0.44, 0.71); Kendalltau-b 0.60 (0.51, 0.69)] and in boys [WK 0.58 (0.47, 0.69), Kendalltau-b 0.50 (0.38, 0.62)]. The correlation between self-reported PDS and rater's assessment was substantial in girls [Kendalltau-b 0.61 (0.54, 0.69)] and moderate in boys [Kendalltau-b 0.49 (0.38, 0.61)]. The Hong Kong Chinese children and adolescents were able to reliably estimate their own sexual maturation status (SMS) using a Chinese version PDS. This instrument may be useful in epidemiological studies when cost, privacy and other concerns preclude the use of other SMS assessment tools.

Body fat measured by bioelectrical impedance in Hong Kong Chinese children.

OBJECTIVE: To establish reference standards for percentage body fat measured in Hong Kong Chinese children, by methods involving bioelectrical impedance analysis. DESIGN: Cross-sectional study. SETTING: Thirty-six randomly selected primary and secondary schools and a teaching hospital in Hong Kong. PARTICIPANTS: A total of 14 842 students randomly selected from the schools and two additional small convenience samples of subjects. MAIN OUTCOME MEASURES: Percentage body fat was measured with the Tanita Body Composition Analyzer (Model no. BF-522) and percentile curves were constructed using the LMS method. In one separate small sample of children, repeatability of the percentage body fat measurement was assessed at different times of the day by BF-522 bioelectrical impedance analysis. In another sample, assessment was by the BF-522 and two other models (BC-418 and BF-401) consecutively to test the agreement of percentage body fat values obtained by the three different models. RESULTS. The percentage body fat values and percentile curves are presented. From the age of 6 to 18 years, the percentage body fat remained fairly stable in boys, but increased steadily in girls. The mean difference in percentage body fat measured with BF-522 at different times of the day was around 1% (95% limits of agreement: -4% to +8%). The mean differences in readings obtained from the BC-418 and BF-522 devices were -3.5% and 1% in boys and girls, respectively. The 95% limits of agreement were particularly wide in boys (-15% to 8%). CONCLUSIONS: Reference values for percentage body fat of Chinese children and adolescents are provided. Caution needs to be exercised however, given that readings obtained at different times of the day vary and data obtained by different makes and models of bioelectrical impedance analysis machines may not be interchangeable.

Grayanotoxin poisoning from Rhododendron simsii in an infant.

We report a case of severe poisoning in a 57-day-old infant who presented with vomiting, convulsions, and shock after ingesting a bottle of milk containing a decoction of Rhododendron simsii. The grandmother collected this toxic plant from a cultivated area, believing it was good for the airways. Grayanotoxin was detected in both the urine and plant specimens. The infant made a good recovery after requiring ventilatory support for 2 days. Rhododendron is a common gardening shrub in Hong Kong. Some Rhododendron species are poisonous and contain grayanotoxin. Intentional or accidental ingestion of toxic plants can be severe or even life-threatening. It is therefore essential that clinicians be familiar with local toxic plant species.

Secular changes in height, weight and body mass index in Hong Kong Children.

BACKGROUND: Large population growth surveys of children and adolescents aged 6 to 18 y were undertaken in Hong Kong in 1963 and 1993. The global epidemic of obesity is a major public health concern. To monitor the impact of this epidemic in Hong Kong children and to identify secular changes in growth, a further growth survey was undertaken in 2005/6. METHODS: Cross-sectional height and weight measurements of 14,842 children and adolescents aged 6 to 18 y from Hong Kong's 18 districts were obtained during the 2005/6 school year. Percentile curves were constructed using LMS method and sex-specific percentile values of weight-for-age, height-for-age, and BMI-for-age were compared with those data from 1963 and 1993. RESULTS: Secular changes in height, weight and BMI were noted between 1963 and 1993 and between 1993 and 2005/6. In the latter period, greater changes were observed at younger ages, and particularly in boys. On an annual basis, the 1993-2005/6 changes were less than those during 1963-1993. Using the International Obesity Task Force cut-offs, 16.7% of children were overweight or obese in 2005/6, which was a 5.1% increase since 1993. CONCLUSION: These data provide policy-makers with further evidence of the secular changes in child growth and the increasing obesity epidemic among Hong Kong children.

Waist circumference and waist-to-height ratio of Hong Kong Chinese children.

BACKGROUND: Central body fat is a better predictor than overall body fat for cardiovascular (CV) risk factors in both adults and children. Waist circumference (WC) has been used as a proxy measure of central body fat. Children at high CV risk may be identified by WC measurements. Waist-to-height ratio (WHTR) has been proposed as an alternative, conveniently age-independent measure of CV risk although WHTR percentiles have not been reported. We aim to provide age- and sex-specific reference values for WC and WHTR in Hong Kong Chinese children. METHODS: Cross sectional study in a large representative sample of 14,842 children aged 6 to 18 years in 2005/6. Sex-specific descriptive statistics for whole-year age groups and smoothed percentile curves of WC and WHTR were derived and presented. RESULTS: WC increased with age, although less after age 14 years in girls. WHTR decreased with age (particularly up to age 14). WHTR correlated less closely than WC with BMI (r = 0.65, 0.59 cf. 0.93, 0.91, for boys and girls respectively). CONCLUSION: Reference values and percentile curves for WC and WHRT of Chinese children and adolescents are provided. Both WC and WHTR are age dependent. Since the use of WHRT does not obviate the need for age-related reference standards, simple WC measurement is a more convenient method for central fat estimation than WHRT.

Comparative study of nasopharyngeal aspirate and nasal swab specimens for diagnosis of acute viral respiratory infection.

Paired nasopharyngeal aspirate (NPA) and nasal swab (NS) samples from 475 children hospitalized for acute respiratory infection were studied for the detection of influenza virus, parainfluenza virus, respiratory syncytial virus, and adenovirus by immunofluorescence test, viral culture, and multiplex PCR assay. The overall sensitivity of viral detection with NPA specimens was higher than that obtained with NS specimens.

Reliability of pubertal self-assessment in Hong Kong Chinese children.

AIM: To validate a Tanner stages self-assessment questionnaire using gender-specific line drawings and brief explanatory text in Chinese. DESIGN: A cross sectional study design. SETTING: One primary and two secondary schools. PARTICIPANTS: 172 boys and 182 girls aged between 8 and 18 years. MAIN OUTCOME MEASURES: Students' self-assessments of pubertal maturation were compared with assessments made by a same gender rater using visual depiction physical examination. Raters' physical examinations were performed after the children had answered the self-assessment questionnaire individually and in private. Raters were blinded to the self-assessment results. Accuracy rates and weighted kappa statistic were used to evaluate the degree of agreement between children and raters. RESULTS: Substantial to almost perfect agreement was found between self- and rater's assessments of breast development and pubic hair growth in girls [weighted kappa 0.72 (P < 0.0001, 95% CI 0.66, 0.79) and 0.83 (P < 0.0001, 95% CI 0.78, 0.87) respectively]. Moderate to substantial agreement was found between self- and rater's assessments of male genital development and pubic hair growth [weighted kappa 0.58 (P < 0.0001, 95% CI 0.48, 0.68) and 0.80 (P < 0.0001, 95% CI 0.74, 0.86) respectively]. Most agreements between self- and rater's assessments differed by only one Tanner stage. Agreement was higher for girls than boys. Girls tended to overestimate their breast stages and boys tended to underestimate their genitalia development. CONCLUSION: This study confirms that a Tanner pubertal self-assessment questionnaire with line drawings and explanatory Chinese text can reliably estimate sexual maturation status in Hong Kong Chinese children.

Predictors for failed dose reduction of inhaled corticosteroids in childhood asthma.

BACKGROUND AND OBJECTIVE: Studies of Western populations have shown that increased exhaled nitric oxide (FeNO) and/or sputum eosinophils (sp-Eos) are predictive of asthma exacerbations. However, the utility of these measurements in different populations and settings is unknown. This study aimed to determine the predictors for failure of reduction of inhaled corticosteroid (ICS) doses in children with stable asthma. METHODS: Fifty children (median age 11.8 years, interquartile range (IQR) 5.9 years) had their dose of ICS halved every 8 weeks until they reached the study end-point (exacerbation or weaned off ICS). Spirometry, FeNO and induced sputum cells were measured at baseline and at each stage of ICS reduction. RESULTS: Eleven subjects suffered an asthma exacerbation and the remainder was successfully weaned off ICS. Subjects with an exacerbation were older (15.4 years (IQR 5.4) vs 11.4 years (IQR 3.9), P = 0.019) and more likely to be boys (P = 0.035). FeNO (median 156 p.p.b. (IQR 131) vs 76.1 p.p.b. (IQR 79.5), P = 0.013) and sp-Eos (17.3% (IQR 33.8%) vs 7.1% (IQR 9.9%), P = 0.019) were significantly greater in those who had an exacerbation. The areas under the receiver operating characteristic curves for FeNO (0.78, 95% CI: 0.59-0.97, P = 0.013) and sp-Eos (0.76, 95% CI: 0.56-0.96, P = 0.016) were similar (P = 0.88) and both were significantly greater than that for FEV(1)% predicted (0.12, 95% CI: 0.08-0.56, P = 0.0013). CONCLUSIONS: Older boys with raised FeNO and sp-Eos are at higher risk of failure of reduction in their ICS dose. Monitoring airway inflammation in children with asthma using FeNO or sp-Eos is clinically useful in guiding ICS dose reduction in a non-Western outpatient setting.

Oscillometrically measured blood pressure in Hong Kong Chinese children and associations with anthropometric parameters.

BACKGROUND: Oscillometric devices are increasingly used to measure blood pressure (BP). Reference data are limited and have not used devices validated against sphygmomanometric measurements on which current standards are based. BP standards for Chinese children have been based on sphygmomanometry and have not provided height-related or weight-related BP percentiles. METHODS: BP was measured in 14842 Hong Kong Chinese schoolchildren aged 6-18 years randomly selected from 36 schools in the 18 Hong Kong districts, using a validated oscillometric device (Datascope Accutorr Plus). Height, weight, heart rate and waist circumference were measured. Percentiles for systolic BP and diastolic BP by sex, age, height and weight were generated. Features associated with systolic BP and diastolic BP in 12680 children were analysed by univariate and multivariate analysis. RESULTS: Reference BP standards by sex, age, weight and height are presented. BP was associated (in descending order of strength) with weight > height > age > waist circumference > body mass index, and weakly with heart rate (which added considerable influence on multivariate analysis). BP increases similarly with age, height (which can normalize for variations in growth) and weight (which is associated most strongly with BP). BP was associated also with family history of high BP and (inversely) with sleep duration. CONCLUSIONS: The study provides oscillometrically measured BP standards for Chinese children, with age-related and sex-related height-specific and weight-specific percentiles. Implications of the findings are discussed. Screening by sex-specific BP-height percentile charts, and then if high, reference to the BP-sex-age-weight table, is suggested.

Assessing disease burden of respiratory disorders in Hong Kong children with hospital discharge data and linked laboratory data.

OBJECTIVES: To describe the pattern of respiratory disorders in the Hong Kong paediatric population admitted to government hospitals, and to assess the reliability of the diagnoses by linkage with laboratory data. METHODS: Discharge diagnoses for all admissions are recorded in a central computerised database, the Clinical Management System. These data were analysed for the inclusive period July 1997 to June 1999. Virology laboratory results from a single hospital were linked to the Clinical Management System diagnostic codes to examine discrepancies in coding specific viral aetiologies. RESULTS: A primary diagnosis of a respiratory disorder was noted in 37.5% (upper respiratory 30.1%, tonsillitis/pharyngitis 10.5%, croup/laryngitis 2.3%, acute otitis media 2.7%, bronchitis/chest infection 2.6%, bronchiolitis 10.2%, pneumonia 20.9%, influenza 4%, asthma and allergic rhinitis 16.5%), and a primary or secondary diagnosis in 42.5% of children younger than 15 years. The incidence rates of respiratory illness coded as bronchiolitis and influenza were respectively estimated to be 887-979 and 222-381 per 100,000 children under 5 years and 3551-3949 and 415-528 per 100,000 children under the age of 1 year. The percentage of respiratory-associated admissions varied significantly by hospital and detailed analysis of data at one hospital highlighted important discrepancies between discharge diagnosis and laboratory results. CONCLUSIONS: These passive surveillance data provide general estimates of the disease burden for respiratory disorders in Hong Kong children. Active surveillance studies are required to provide more accurate estimates of the disease burden. Consideration should be given to enhance the Clinical Management System by routinely linking all laboratory data with discharge diagnosis information, by establishing sentinel surveillance hospitals and by assessing new strategies to standardise coding.

Serotype distribution and antimicrobial susceptibilities of nasopharyngeal isolates of Streptococcus pneumoniae from children hospitalized for acute respiratory illnesses in Hong Kong.

Five hundred nineteen Streptococcus pneumoniae isolates from nasopharyngeal aspirates of 3,157 children (age, <16 years) participating in a respiratory surveillance study in Hong Kong in 2005 and 2006 indicated that 64.9% and 37.2% of the isolates were not susceptible to penicillin and cefotaxime, respectively. The rate of potential coverage by the seven-valent conjugate vaccine was 72.3%, and the rate increased to 74.6% for serogroup-specific types.