Normative data for quantitative calcaneal ultrasound in Asian children

<p><b>INTRODUCTION</b>Dual energy X-ray absorptiometry (DEXA) is currently the gold standard for the assessment of bone mineral density. Quantitative ultrasound (QUS), on the other hand, is a radiation-free alternative for the assessment of bone strength in the paediatric population. Establishing normative data for bone strength specific to the population would allow identification of children at risk of osteoporosis as a consequence of disease and its treatment. This cross-sectional study aims to establish the normal reference range for calcaneal broadband ultrasound attenuation (BUA) measurements in normal Singaporean children aged 6 to 12 years.</p><p><b>MATERIALS AND METHODS</b>Healthy Singaporean children were randomly selected from 11 primary schools for the assessment of calcaneal BUA, using the paediatric Contact Ultrasonic Bone Analyzer (CUBA, McCue Plc, Compton, Winchester, England). The height, weight, body mass index and BUA measurements for each age group and gender were expressed as the mean ± SD. One-way ANOVA was used to compare the mean calcaneal BUA by age and gender of Singaporean children with that of children from the United Kingdom, Turkey and Taiwan.</p><p><b>RESULTS</b>A total of 750 healthy Singaporean children (417 males and 333 females) aged 6 to 12 years from 11 primary schools were enrolled. The calcaneal BUA values of Turkish and white British children were not statistically different from this Singaporean cohort. However, the Singaporean calcaneal BUA measurements were significantly higher compared to the Taiwanese children.</p><p><b>CONCLUSION</b>This study provides the first normal reference data to evaluate bone strength in Singaporean children using the paediatric Contact Ultrasonic Bone Analyzer.</p>

Diagnostic accuracy of anthropometric indices for obesity screening among Asian adolescents

<p><b>INTRODUCTION</b>Weight-and-height-based anthropometric indices have long been used for obesity screening among adolescents.However, the ability of their age-and-sex-specific reference values in classifying adolescent as "obese" in different populations was not fully established. Our study aimed to validate the existing international (BMI-for-age charts from WHO, CDC, IOTF) and local cut-offs [percent weight for height (PWH)] for obesity against body fat percentage, as assessed by 4 skinfolds measurement.</p><p><b>MATERIALS AND METHODS</b>A cross-sectional sample of 6991 adolescents aged 12 to 18 years was measured. All anthropometric measurements were compliant with the internationally accepted protocol. Obesity was defined as percentage body fat greater than or equal to 95 percentile, specific to age and sex. The validity of the existing classification criteria in detecting obesity was evaluated by comparing their respective diagnostic accuracy.</p><p><b>RESULTS</b>Both prevalence of obesity and diagnostic accuracy indices varied by the classification criteria. While all criteria generated very high specificity rates with the lowest being 95%, their sensitivity rates were low ranging from 43% to 71%. Youden's index suggested that CDC and WHO criteria had optimal sensitivity and specificity. ROC analysis showed that overall performance could be improved by refining the existing cut-offs.</p><p><b>CONCLUSIONS</b>Clinical validity of weight-and-height-based classification systems for obesity screening in Asian adolescents is poorer than expected, and this could be improved by refining the existing cut-offs.</p>

3rd College of paediatrics and child health lecture--the past, the present and the shape of things to come

The growth trends of Singapore children spanning 5 decades are reviewed, based on 8 anthropometric studies from 1957 till 2002. The heights of pre-school children and school age children appear to have optimised according to their genetic potential, but the weights and body mass indices of children still appear to be increasing from 6 to 18 years for both sexes, probably as a consequence of increasing affluence. This trend is reflected in the increasing obesity prevalence in school children over the past 30 years, and the concomitant increased morbidity associated with the metabolic syndrome, necessitates further research into the causes of obesity. Barker's hypothesis first suggested that changes in the intra-uterine environment can cause fetal adaptations which persist into adulthood, and are responsible for many chronic diseases of adult life. More recently, intense research in the field of epigenetics suggests that the environment can also influence the phenotype through gene expression, through modification of DNA methylation and histones which, in turn, influences gene expression. The challenge for the future is to determine if there are clear epigenetic changes, which are responsible for the increased prevalence of childhood and adolescent obesity, and whether these changes are transmitted through generations. Unravelling these epigenetic mechanisms may be the key to the prevention of obesity and the metabolic syndrome.

Clinical applications of molecular genetics: the model of congenital adrenal hyperplasia

Spectacular advances in molecular genetics have enabled the molecular characterisation of many genetic disorders. The clinical applications include: (i) identification of pre-symptomatic and symptomatic affected individuals (monogenic diseases), allowing for early treatment and prevention of complications, (ii) carrier testing for genetic counselling, (iii) pharmacogenetic testing to guide medical treatment, and (iv) susceptibility testing (in polygenic diseases) to determine the risk of developing future disease. Using the model of congenital adrenal hyperplasia (CAH), direct mutational analysis can be applied to: (i) confirm the diagnosis when hormone assays have been equivocal, which would allow for early treatment and prevention of adrenal crisis, (ii) prenatal diagnosis and prenatal treatment in affected females to prevent or reduce prenatal virilisation, (iii) heterozygote carrier identification for genetic counselling, (iv) novel therapeutic applications to optimise treatment, including adjusting the steroid dose based on consistent genotype-phenotype correlations, so as to reduce the incidence of growth-inhibiting effects of steroid excess. However, molecular analysis can occasionally be complicated by multiple mutations on one allele, which may potentially affect genotype-phenotype correlations. Hence, molecular genetic analysis of CAH may eventually be adopted as a second tier confirmation of the disease, but is unlikely to replace the current first tier screening assays of precursor steroid metabolites proximal to the enzyme deficiency.