Urinary calcium excretion in healthy children and adolescents

Urinary calcium (Ca) excretion was determined in 1,578 24-h urine samples from 507 healthy children and adolescents (252 boys, 255 girls; 2.8–18.4 years) participating in the DONALD Study and is presented for 32 different age and sex groups. Calciuria values related to body weight (mg/kg per day) were relatively constant except for a transient decrease during puberty in all centiles, with a later onset in boys than girls. Distribution of calciuria (mg/kg per day) was best normalized by log transformation, with an almost constant standard deviation of the log-transformed values. Ca excretion was ≥4 mg/kg per day in 8.6% and ≥6 mg/kg per day in 1.5% of the urine samples. Based on Ca excretion rates of 1,080 pairs of 24-h urine samples from 364 children and adolescents, sensitivity, specificity, and the predictive value for hypercalciuria (≥4 mg/kg per day) in the next urine sample were calculated at three test levels classifying calciuria of the initial urine sample. In summary, this study presents normal values of urinary Ca excretion related to age and sex in a population of healthy German children and adolescents consuming a typical western-style diet. A high level of calciuria in a random urine sample is important in the diagnosis of hypercalciuria. Received: 25 February 1997 / Revised: 28 April 1999 / Accepted: 3 May 1999     

Urinary creatinine excretion and protein/creatinine ratios vary by body size and gender in children

Urinary protein/creatinine ratio (Up/cr) is a simple measurement for evaluation of proteinuria. However, exact effects of body size and gender on urinary excretion of creatinine and Up/cr remain unknown. We aimed to clarify their effects. Early morning urine samples were collected from 124 children with urinary tract disorders. Urinary hourly excretion of creatinine, Ucr (in milligrams per hour), urinary hourly excretion of protein per body surface area, Up (milligrams per square meter per hour), and Up/cr (milligrams per milligram) were calculated. Effects of gender, age, body height, body weight and body surface area on Ucr and Up/cr were analyzed, respectively, in a multiple linear regression model. Body surface area and gender affected Ucr (r²=0.842, P<0.0001). Ucr adjusted by body surface area increased as body surface area grew with moderate variation. Up/cr showed a close correlation with Up and was affected by body height and gender as well. The regression equation showed that Up/cr values corresponding to the normal upper limit of Up, i.e., 4 mg/m²/h, in boys and girls 170 cm tall were approximately one third of those in children 80 cm tall (0.121 vs 0.043 for boys, 0.132 vs 0.047 for girls). The present study indicates that estimation of Up/cr needs to include consideration of children’s body height and gender.     

Factors affecting renal hydrogen ion excretion capacity in healthy children

In 560 healthy German children and adolescents aged 2.8–22.0 years from the DONALD (Dortmund Nutritional and Anthropometric Longitudinally Designed) study, the relationship between urine pH and renal net acid excretion (mmol/day/1.73 m²) was analysed. A quadratic model showed the best fit (r ²=0.608). Using logistic regression analysis three parameters (urinary phosphorus excretion, total protein intake and urinary ratio of potassium and sodium) had a significant effect on renal hydrogen ion excretion capacity characterised by the probability of high or low net acid excretion with respect to the urine pH value. Urinary osmolality, in contrast to what has been seen in a previous experimental study with low birth weight infants, along with sex and age had no significant independent effects on renal net acid excretion with respect to the urine pH value over the range of osmolalities observed. In healthy children and adolescents a low fluid intake with high urinary osmolality does not at least substantially decrease the renal capacity of hydrogen ion excretion. Received: 7 April 2000 / Revised: 15 December 2000 / Accepted: 15 December 2000     

Calcium accretion in girls and boys during puberty: a longitudinal analysis.

The primary purpose of this study was to estimate the magnitude and variability of peak calcium accretion rates in the skeletons of healthy white adolescents. Total-body bone mineral content (BMC) was measured annually on six occasions by dual-energy X-ray absorptiometry (DXA; Hologic 2000, array mode), a BMC velocity curve was generated for each child by a cubic spline fit, and peak accretion rates were determined. Anthropometric measures were collected every 6 months and a 24-h dietary recall was recorded two to three times per year. Of the 113 boys and 115 girls initially enrolled in the study, 60 boys and 53 girls who had peak height velocity (PHV) and peak BMC velocity values were used in this longitudinal analysis. When the individual BMC velocity curves were aligned on the age of peak bone mineral velocity, the resulting mean peak bone mineral accrual rate was 407 g/year for boys (SD, 92 g/year; range, 226-651 g/year) and 322 g/year for girls (SD, 66 g/year; range, 194-520 g/year). Using 32.2% as the fraction of calcium in bone mineral, as determined by neutron activation analysis (Ellis et al., J Bone Miner Res 1996;11:843-848), these corresponded to peak calcium accretion rates of 359 mg/day for boys (81 mg/day; 199-574 mg/day) and 284 mg/day for girls (58 mg/day; 171-459 mg/day). These longitudinal results are 27-34% higher than our previous cross-sectional analysis in which we reported mean values of 282 mg/day for boys and 212 mg/day for girls (Martin et al., Am J Clin Nutr 1997;66:611-615). Mean age of peak calcium accretion was 14.0 years for the boys (1.0 years; 12.0-15.9 years), and 12.5 years for the girls (0.9 years; 10.5-14.6 years). Dietary calcium intake, determined as the mean of all assessments up to the age of peak accretion was 1140 mg/day (SD, 392 mg/day) for boys and 1113 mg/day (SD, 378 mg/day) for girls. We estimate that 26% of adult calcium is laid down during the 2 adolescent years of peak skeletal growth. This period of rapid growth requires high accretion rates of calcium, achieved in part by increased retention efficiency of dietary calcium.     

A new approach to the diagnosis of children’s urolithiasis based on the Bonn Risk Index

Published data on the association between calcium oxalate (CaOx) crystallization and kidney stone disease in children are scarce. The aims of this study were to determine CaOx crystallization using the Bonn Risk Index (BRI) in children with urolithiasis in comparison to healthy controls, to evaluate the relationships between BRI and urinary parameters, such as pH, calciuria, oxaluria and citraturia, and to assess the association between BRI and the size of renal stones. We compared the BRI in 142 Caucasian children and adolescents (76 girls, 66 boys) aged 3-18 years with kidney stones and 210 healthy age- and sex-matched controls without urolithiasis. Urinary ionized calcium ([Ca2+]) was measured using a selective electrode, while the onset of spontaneous crystallization was determined using a photometer and titration with 40 mmol/L ammonium oxalate (Ox2-). The calculation of the BRI value was based on the Ca2+:Ox2- ratio. High-resolution renal ultrasonography was carried out to estimate the size of the renal stones. The BRI values were 15-fold higher in children with renal stones than in healthy children without stones. The same trend was shown by BRI/kg body weight (tenfold greater in children with renal stones than in healthy children without stones), BRI/per 1.73 m2 body surface (13-fold greater) and BRI/body mass index (23-fold greater). No association was observed between BRI and the diameter of stones. Children with kidney stones, both males and females, had an increased BRI compared with subjects without urolithiasis. High BRI suggests an association with lower urinary pH, hypercalciuria, hyperoxaluria or hypocitraturia, which are all risk factors of kidney stones. An increased BRI in children, although unrelated to renal stone size, reflects the risk of calcium oxalate crystallization and may indicate early metabolic disorders leading to urolithiasis.     

Reference values of plasma oxalate in children and adolescents

Oxalate homeostasis is a derivative of absorption and transportation in the digestive system and renal/intestinal excretion of oxalate. The objective of this cross-sectional study was to determine normative values of plasma oxalate in relation to age, gender, and body size. A group of 1,260 healthy Caucasian children and adolescents aged 3 months to 18 years [mean +/- standard deviation (SD) 10.5 +/- 4.3] was studied. Each 1-year group comprised 70 subjects. Oxalate levels were assessed in blood plasma samples obtained from fasted individuals using the precipitation-enzymatic method with oxalate oxidase. Median oxalate levels in healthy infants was 3.20 micromol/L (5th-95th percentiles: 1.56-5.58) and was higher compared with older children [2.50 micromol/L (5th-95th percentiles: 0.95-5.74); p < 0.01]. No differences were found in plasma oxalate levels between boys and girls. There were no associations between plasma oxalate levels and anthropometric traits. In the healthy population aged 1-18 years, plasma oxalate concentration is independent of age, gender, and body size. Infants demonstrate higher plasma oxalate levels compared with older children, which suggests possible immature mechanisms of renal excretion. This study appears to be the first extensive report providing normative data for plasma oxalate in children and adolescents.     

Step Counts and Body Mass Index Among 9-14 Years Old Greek Schoolchildren

The main purpose of this study was the identification of the current pedometer determined physical activity levels of a large sample of 9 -14 years old Greek schoolchildren and the determination of the association between daily step counts and body mass index through the comparison of step counts among overweight, obese and normal-weight children. A total of 532 children (263 boys and 269 girls) were measured for height and weight. Their activity levels were analyzed using pedometers to measure mean steps for 7 consecutive days. Overweight and obese status was determined using the international reference standard (Cole et al., 2000). According to data analysis mean step counts ranged from 15371 to10539 for boys and from 11536 to 7893 for girls. Steps per day were significantly more for boys compared to girls. Children with normal weight performed significantly more steps per day compared to their overweight and obese classmates. Daily step counts reported in this study for 9 -14 year old schoolchildren were relatively low when compared to step counts from other European countries. Only 33.9% of the participants satisfied the body mass index referenced standards for recommended steps per day. Finally, the results of this study provide baseline information on youth pedometer determined physical activity and on youth body mass index levels. High prevalence of low daily step counts and BMI determined obesity was revealed prompting for further exploration of the relationship between objectively measured physical activity and adiposity in particular for children and adolescents that experience both health risk factors.

Key points

• The mean steps/day taken by both boys and girls in Greece 9-14 years old were 13.446 and 10.656 respectively.
• Daily step counts tended to be leveled for ages 9-12 years and a significant drop in steps/day was apparent for children aged 13 -14 years.
• According to the IOTF criteria, 23% of the boys that participated in this study were overweight and 7.8% were obese, while in girls the respective rates were 24.8% and 4.7%.
• Children with normal weight performed significantly more steps/day than the overweight and the obese children.

Key words: Childhood, obesity, pedometry     

Abundance and activity of Ca2+-ATPase in hypercalciuric children

The plasma membrane Ca²⁺-ATPase (PMCA) is one of the main regulators of cell Ca²⁺ homeostasis. The aim of our study was to determine whether the abundance and activity of PMCA are altered in erythrocytes of children with idiopathic hypercalciuria. Twenty-four children with idiopathic hypercalciuria (13 girls and 11 boys, mean age 10.6±4.8 years; mean urinary calcium concentration 0.85±0.20 mmol/mmol creatinine) and 30 healthy age-matched children were enrolled. PMCA protein abundance was determined by Western blot analysis. Enzyme activity was determined spectrophotometrically. The abundance of PMCA did not differ in hypercalciuric patients from that of control subjects (98±22% vs 100±18%). Moreover, the activity was not different between the studied groups (3141±1494 vs 2953±780 nmol ATP/mg protein/h). The extent of hypercalciuria did not correlate with enzyme abundance or activity. Assuming that erythrocytes may reflect the renal tubular transporting processes, our data suggest that other Ca²⁺-transport mechanisms than PMCA might be involved in the development of idiopathic hypercalciuria in children. Received: 5 December 2000 / Revised: 2 May 2001 / Accepted: 3 May 2001     

Long-term effects of growth hormone treatment on growth and puberty in patients with chronic renal insufficiency

Several prospective trials have shown that recombinant human growth hormone (GH) accelerates growth significantly during the first years of therapy, but the effects of long-term GH therapy with regard to long-term growth response and safety have not yet been established. Forty-five Dutch prepubertal children [28 boys, 17 girls, mean (SD) age 7.8 (3.4) years] with chronic renal insufficiency (CRI) and severe growth retardation started GH therapy between 1988 and 1991 within one of the randomized Dutch trials. Long-term GH therapy, in this study a maximum of 8 years, resulted in a sustained and significant improvement of height standard deviation score (SDS) compared with baseline values (P<0.001). The mean height SDS reached the lower end (-2 SDS) of the normal growth chart after 3 years of GH therapy. During the following years the mean height SDS gradually increased, thereby approaching the mean target height SDS after 6 years of GH therapy. Three factors were significantly associated with the height SDS after 4 years of GH therapy: height SDS at the start (+) of therapy, age at the start of therapy (-), and the duration of dialysis treatment (-). Bone maturation did not accelerate during long-term GH therapy. Children on a conservative regimen at the start of GH therapy had no accelerated deterioration of renal function during 6 years of GH therapy. The average daily GH dose administered over the years had no significant influence on the glomerular filtration rate after 4 years. GH therapy had no adverse effects or significant effect on parathyroid hormone concentration, nor were there any radiological signs of renal osteodystrophy. Puberty started at a median age, within the normal range, of 12.4 years in boys and 12.0 years in girls, respectively. Long-term GH therapy leads to a sustained improvement in height SDS in children with growth retardation secondary to CRI, resulting in a normalization of height in accordance with their target height SDS, without evidence of deleterious effects on renal function or bone maturation. A GH dosage of 4 IU/m² per day appears efficient and safe. Our long-term data show that final height will be within the normal target height range when GH therapy is continued for many years. Received: 25 March 1999 / Revised: 13 January 2000 / Accepted: 20 January 2000     

1024例儿童尿流率调查

目的 寻求长沙地区儿童尿流率正常值及其列线图。方法 对1024名正常儿童进行1048次尿流率检测。将所得资料按性别、年龄、体表面积、排尿量分组后进行统计学分析，并绘制出各组相应的列线图以阐明尿量、体表面积、平均尿流率、最大尿流率4者的相互关系。结果 正常儿童尿流率曲线为典型的钟形曲线。〈7岁男性儿童的最大尿流率随年龄增加而增加，年龄每增加1岁最大尿流率增加1．7ml／s，〉7岁者其最大尿流率同成年人相仿。〈9岁女性儿童的最大尿流率随年龄增加而增加，年龄每增加1岁最大尿流率增加1．2ml／s，〉9岁其最大尿流率同成年人相近。儿童最大尿流率、平均尿流率及排尿量均随体表面积增加而增加，同时，最大尿流率、平均尿流率也均随排尿量的增加而增加。结论 〈9岁的女童和〈7岁的男童最大尿流率的正常值有明显的年龄依从性。     

Regional and total body bone mineral content,bone mineral density,and total body tissue composition in children 8–16 years of age

Summary Normative values for total body bone mineral content (TBBM) and total body bone mineral density (TBMD) were derived from measurements on 234 children 8–16 years of age. In addition, bone mineral content (BMC) and bone mineral density (BMD) values for selected regions of interest and soft tissue (bone free lean and fat) for the total body are presented. Bone mineral and soft tissue values were determined by dual energy X-ray absorptiometry (DXA) using a Hologic QDR-2000 in the array mode. Results of a stepwise multiple regression analysis revealed a significant correlation between bone-free lean tissue (BFLT) and BMD (r² = 0.80) in girls. Adding age to the equation accounted for an additional 2% of the variance (P < 0.05) and height accounted for another 1% of the variance (P < 0.05). Body weight and fat tissue (FT) did not account for any additional variance. In boys BFLT correlated significantly with BMD (r² = 0.75;P < 0.05); none of the other predictor variables accounted for additional variance. No significant differences were found in TBBM or TBMD between boys and girls at any age. There was a significant overall gender effect for only three regions of interest. Boys had greater BMC in the head region and had greater BMD in the upper limbs, but post hoc analysis revealed no significant differences for any specific age groups. Girls had greater overall BMD in the pelvis, but this difference was only significant at the 15–6-year age group. The changes in BFLT and FT over the age ranges were consistent with the growth literature.The normative values can be applied to the assessment of children and adolescents with health problems that may impact on the skeleton as well as to research studies investigating bone mineral development in children.     

Age trends of bone mineral density and percentile curves in healthy Chinese children and adolescents

The clinical utility of dual-energy X-ray absorptiometry (DXA) measurement requires appropriate normative values, designed to be diverse with respect to age, gender and ethnic background. The purpose of this study was to generate age-related trends for bone density in Chinese children and adolescents, and to establish a gender-specific reference database. A total of 1,541 Chinese children and adolescents aged from 5 to 19-years were recruited from southern China. Bone mineral density (BMD), bone mineral content (BMC), and bone area (BA) were measured for the total body (TB) and total body less head (TBLH). The height-for-age, height-for-BA, and BMC-for-BA percentile curves were developed using the least mean square method. TB BMD and TBLH BMD were highly correlated. After 18 years, TB BMD was significantly higher in boys than girls. For TB BMC and TBLH BMC, gender differences were found in age groups 12 years and 16–19 years; however, the TBLH BMD was significantly different between genders >16 years. The head region accounted for 13–52 and 16–49 % of the TB BMC in boys and girls, respectively. Furthermore, the percentages were negatively correlated with age and height. This study describes a gender-specific reference database for Chinese children and adolescents aged 5–19 years. These normative values could be used for clinical assessment in this population.     

Spinal Overload: A Concern for Obese Children and Adolescents?

Heavy children require stronger bones than leaner children. The present cross-sectional observational study was undertaken to examine the magnitude of compensatory increases in the spinal bone mineral content (BMC) and area shown by overweight and obese children and adolescents. Vertebral area and BMC of lumbar vertebrae L2–L4 were measured by dual-energy X-ray absorptiometry in 202 boys and 160 girls aged 3–19 years. Subjects were categorized as of normal weight, overweight or obese using international cutoffs for body mass index. Compared with children of healthy weight our overweight and obese children had lower vertebral BMC for their bone area, body height, body weight and pubertal development: ratios and 95% CI for overweight and obese groups were 0.92 (95% CI 0.87–0.97) and 0.88 (95% CI 0.80–0.96) for girls and 0.96 (95% CI 0.91–1.02, NS) and 0.87 (95% CI 0.78–0.96) for boys, respectively. Spinal area was low in overweight and obese girls compared with girls of healthy weight but overweight and obese boys had enlarged their vertebral area appropriately for their increased body size. We conclude that during growth overweight and obese children do not increase their spinal BMC to fully compensate for their excessive weight. Limiting excessive adiposity in childhood and adolescence should help to avoid excessive loading and stresses on the lumbar spine. Received: 20 November 2001 / Accepted: 20 May 2002     

Calcaneal Ultrasound Imaging in Healthy Children and Adolescents: Relation of the Ultrasound Parameters BUA and SOS to Age, Body Weight, Height, Foot Dimensions and Pubertal Stage

We investigated the quantitative ultrasound (QUS) parameters broadband ultrasound attenuation (BUA) and speed of sound (SOS) measured in the posterior part of the calcaneus at the region of interest (ROI) with the lowest attenuation, using an ultrasound imaging device (UBIS 3000) in 491 healthy Caucasian children and adolescents (262 girls, 229 boys) between 6 and 21 years old. The relation of age, body weight, height, foot dimensions and pubertal stage to BUA and SOS was assessed. BUA increased nonlinearly with age in boys and girls, r ² being 0.44 (p<0.001) and 0.57 (p<0.001), respectively. SOS increased linearly with age in girls (r ²= 0.04, p<0.001). There was no significant increase in SOS in boys (r ²= 0.01, p>0.05). Heel width was significantly correlated with BUA (r= 0.20, p<0.005 in boys; r= 0.27, p<0.05 in girls) and with SOS (r=−0.19, p<0.005 in boys; r=−0.08, p<0.05 in girls). After downward adjustment of the ROI size according to foot length quartiles, significantly lower BUA and SOS values were found compared with those with the standard ROI size of 14 mm. After correction for heel width and adjustment of the ROI size based on foot length, BUA and SOS were significantly associated with age in boys (r ²= 0.36, p<0.001 and 0.06, p<0.05) and in girls (r ²= 0.53 and 0.06, both p<0.001). Tanner stage was significantly correlated with BUA (r= 0.62, p<0.001 in boys; r= 0.73, p<0.001 in girls) but not with SOS. BUA but not SOS increased significantly with the number of years since menarche (p<0.001). In a multiple stepwise regression analysis in boys, age, weight and foot length were independent predictors for BUA, and age and foot length for SOS. In girls, age and weight were independent predictors for BUA and age was the only independent predictor for SOS. After correction for age, pubertal stages and heel width were no longer determinants for QUS parameters in either boys or girls. In conclusion, BUA increased significantly with age in both sexes. SOS increased with age in both boys and girls, but the increase was small and not statistically significant in boys. SOS, as measured with the UBIS 3000 device, may therefore not be appropriate to assess skeletal status in healthy children. Whether SOS and BUA are affected in children with skeletal disorders has yet to be determined. In boys, age, weight and foot length were independent predictors for BUA and age and foot length for SOS. In girls, age and weight were independent predictors for BUA and age was the only independent predictor for SOS. In our opinion, children with small feet should be measured with a smaller ROI diameter than those with larger feet. Received: 28 October 1999 / Accepted: 19 June 2000     

Total body water volume for white children and adolescents and anthropometric prediction equations: the Fels Longitudinal Study

BACKGROUND: There are few studies of total body water (TBW) volume in children. Such studies are needed, as are new prediction equations for the clinical management of children with renal insufficiency and those receiving dialysis. METHODS: Mixed longitudinal data were from 124 white boys and 116 white girls 8 to 20 years of age. TBW volume was measured by deuterium nuclear magnetic resonance spectroscopy, and random effects models were used to determine patterns of change over time. Sex-specific TBW prediction equations were developed using regression analysis. RESULTS: Boys had significantly greater (P < 0.05) mean TBW volumes than girls at all but 3 ages. TBW was significantly (P < 0.05) associated with age and maturation in the boys and the girls. In boys, mean TBW/WT varied from 0.55 to 0.59, while in the girls the mean declined from 0.53 to 0.49 by 16 years of age. Boys had significantly larger means for TBW/WT than girls, who had a significant, slight negative trend with age. The prediction equations were TBW = -25.87 + 0.23 (stature) + 0.37 (weight) for boys and TBW =-14.77 + 0.18 (stature) + 0.25 (weight) for girls. CONCLUSION: Means are provided for TBW in white children from 8 to 20 years of age, whose average fatness affected the percentage of TBW in body weight. These updated TBW prediction equations perform better than those available from the past.     

Vitamin D3 Dose Requirement to Raise 25‐Hydroxyvitamin D to Desirable Levels in Adolescents: Results from a Randomized Controlled Trial

Several organizations issued recommendations on desirable serum 25‐hydroxy vitamin D [25(OH)D] levels and doses of vitamin D needed to achieve them. Trials allowing the formulation of evidence‐based recommendations in adolescents are scarce. We investigated the ability of two doses of vitamin D₃ in achieving recommended vitamin D levels in this age group. Post hoc analyses on data from a 1‐year double‐blind trial that randomized 336 Lebanese adolescents, aged 13 ± 2 years, to placebo, vitamin D₃ at 200 IU/day (low dose), or 2000 IU/day (high dose). Serum 25(OH)D level and proportions of children achieving levels ≥20 ng/mL and 30 ng/mL were determined. At baseline, mean 25(OH)D was 15 ± 7 ng/mL, 16.4 ± 7 ng/mL in boys, and 14 ± 8 ng/mL in girls, p = 0.003, with a level ≥20 ng/mL in 18% and ≥30 ng/mL in 5% of subjects. At 1 year, mean levels were 18.6 ± 6.6 ng/mL in the low‐dose group, 17.1 ± 6 ng/mL in girls, and 20.2 ± 7 ng/mL in boys, p = 0.01, and 36.3 ± 22.3 ng/mL in the high‐dose group, with no sex differences. 25(OH)D increased to ≥20 ng/mL in 34% of children in the low‐dose and 96% in the high‐dose group, being higher in boys in the low‐dose arm only; it remained ≥30 ng/mL in 4% of children in the low‐dose arm but increased to 64% in the high‐dose arm. Baseline 25(OH)D level, body mass index (BMI), and vitamin D dose assigned were the most significant predictors for reaching a 25(OH)D level ≥20 ng/mL and 30 ng/mL. A daily dose of 2000 IU raised 25(OH)D level ≥20 ng/mL in 96% of adolescents (98% boys versus 93% girls). Dose‐response studies are needed to determine in a definitive manner the daily allowance of vitamin D for Middle Eastern adolescents with a similar profile. © 2014 American Society for Bone and Mineral Research.     

Normative data and percentile curves for Dual Energy X-ray Absorptiometry in healthy Indian girls and boys aged 5-17 years

For the correct interpretation of Dual Energy X-ray Absorptiometry (DXA) measurements in children, the use of age, gender, height, weight and ethnicity specific reference data is crucially important. In the absence of such a database for Indian children, the present study aimed to provide gender and age specific data on bone parameters and reference percentile curves for the assessment of bone status in 5-17 year old Indian boys and girls. A cross sectional study was conducted from May 2006 to July 2010 on 920 (480 boys) apparently healthy children from schools and colleges in Pune City, India. The GE-Lunar DPX Pro Pencil Beam DXA scanner was used to measure bone mineral content (BMC [g]), bone area (BA [cm(2)]) and bone mineral density (BMD [g/cm(2)]) at total body, lumbar spine and left femur. Reference percentile curves by age were derived separately for boys and girls for the total body BMC (TBBMC), total body BA (TBBA), lumbar spine bone mineral apparent density (BMAD [g/cm(3)]), and left femoral neck BMAD. We have also presented percentile curves for TBBA for height, TBBMC for TBBA, LBM for height and TBBMC for LBM for normalizing bone data for Indian children. Mean TBBMC, TBBA and TBBMD were expressed by age groups and Tanner stages for boys and girls separately. The average increase in TBBMC and TBBA with age was of the order of 8 to 12% at each age group. After 16 years of age, TBBMC and TBBA were significantly higher in boys than in girls (p<0.01). Maximal increase in TBBMD occurred around the age of 13 years in girls and three years later in boys. Reference data provided may be used for the clinical assessment of bone status of Indian children and adolescents.     

Effect of malnutrition on serum creatinine and cystatin C levels

The concentration of cystatin C has been shown to be independent of age, gender and height, but the effect of malnutrition has not been studied. Levels of serum creatinine and cystatin C were estimated in 77 malnourished and 77 normally nourished boys between 2 years and 6 years of age without evidence of renal disease. The mean (95% confidence interval) serum creatinine level in the malnourished boys was significantly lower than that in the normally nourished boys [0.42 (0.38–0.45) mg/dl and 0.51 (0.48–0.55)] mg/dl, respectively, (P < 0.01)]. The mean level of serum cystatin C was 1.05 (0.94–1.17) mg/l and 1.12 (1.01–1.24) mg/l, respectively, in normally nourished and malnourished boys (P = 0.35). Mean glomerular filtration rate (GFR) estimated by the Schwartz equation in the malnourished boys was significantly higher than that in normally nourished children [141.8 (123.3–160.2) ml/min per 1.73 m² body surface area and 119.4 (109.3–129.5) ml/min per 1.73 m² body surface area], respectively (P = 0.04). However, the mean cystatin C-derived GFR was similar in the malnourished and normally nourished boys [99.70 (85.8–113.5) ml/min per 1.73 m² and 109.2 (94.4–124.0) ml/min per 1.73 m²], respectively (P = 0.35). The mean bias between GFR estimates using Bland and Altman analysis was greater in the malnourished children than in the normally nourished children (32.3% and 17.6%, respectively) (P = 0.15). Serum creatinine levels are lower in malnourished children and lead to overestimation of GFR, while cystatin C levels are unaffected.     

Reference equations for ultrasound bone densitometry of the radius in Central European children and adolescents

Summary

Bone density measurements are important for evaluation and follow-up of children with alterations in their mineral status (increased risk for fractures and osteoporosis subsequently). Interpretation of these measurements relies on the availability of appropriate reference equations. We developed gender-specific, age-dependent reference values of bone density for Central European children.

Introduction

In recent years, there has been an increasing demand for the measurement of bone density in children exposed to an increased risk of early alterations in their bone status. These values must be compared to an adequate reference population. The aim of the present study was to create reference equations of radial speed of sound (SOS) for Central European children and adolescents.

Methods

In this cross-sectional study, SOS values were measured at the distal third of the radius in 581 Swiss children and adolescents (321 girls and 260 boys) aged 6 to 16 years using the Sunlight Omnisense® 7000P quantitative ultrasound system.

Results

Gender-specific reference equations for SOS values were derived by polynomial regression and combined a cubic dependence of age and a linear dependence of height. The fitted SOS curves in our study population show a plateau period in both genders for younger ages followed by an increase phase beginning at the age of 12 in girls and 14 in boys. Neither the reported level of physical activity nor additional sport nor self-reported calcium intake influenced the reference equations.

Conclusions

Our results show a good agreement with similar studies using the same measurement technique on other body parts, suggesting a wide applicability of the obtained reference curves over different European populations.