Sydney Diabetes centre's experience of the Australian Government's roll out of subsidised continuous glucose monitoring for children with type 1 diabetes mellitus

AIM

To determine patient/carer expectations of continuous glucose monitoring (CGM) and short-term satisfaction, to assess the efficacy of CGM in improving: fear of hypoglycaemia and glycaemic control (HbA_1c , ketosis, hypoglycaemia) and to determine time requirements of diabetes clinic staff in commencing and administering CGM.

METHODS

We assessed CGM-naïve patients starting on CGM at a Sydney Diabetes Centre following the introduction of a nationwide government subsidy for CGM. A standardised questionnaire was administered collecting demographic and glycaemic information in addition to Likert scale assessment of expectations and satisfaction. Clinic staff reported time dedicated to CGM education, commencement and follow-up.

RESULTS

A total of 55 patients or parents/carers completed baseline questionnaires, with 37 completing a 3-month follow-up questionnaire. There were high expectations of CGM prior to commencement and high satisfaction ratings on follow-up. CGM improved fear of hypoglycaemia, and total daily insulin dose increased after commencement of CGM. There was a trend towards lower HbA_1c that was not statistically significant and no statistically significant reduction in ketosis or hypoglycaemia. Comments were mostly positive, with some concern raised regarding technical issues and a lack of subsidy after 21 years of age. Staff time requirements were substantial, with an estimated average of 7.7 h per patient per year.

CONCLUSIONS

Patients and families have high expectations of CGM, and satisfaction levels are high in the short term. Total insulin delivery increased after CGM commencement. Time requirements by staff are substantial but are worthwhile if families' overall satisfaction levels are high.

A pilot randomized controlled trial of a post-discharge program to support emerging adults with type 1 diabetes mellitus transition from pediatric to adult care

AIMS

There is a paucity of randomized controlled trials (RCT) examining transition from pediatric to adult care in type 1 diabetes mellitus (T1DM). This study aimed to determine if transition in T1DM is more effective with a comprehensive transition program (CTP) compared with standard clinical practice (SCP).

METHODS

This RCT recruited as young people left pediatric diabetes services. The trial co-ordinator provided CTP participants with standardized telephone communication support at week 1, and 3, 6, and 12 months post-discharge from pediatric care. SCP participants were briefly contacted at 6 and 12 months post-discharge to confirm transfer status; they received no other post-discharge contact as per usual practice. At 12 months, the primary outcomes were engagement and retention in the adult service and secondary outcomes included hemoglobin A1c (HbA1c), diabetes-related hospitalizations, microvascular complication appearance, and global self-worth.

RESULTS

Most CTP participants (11/14) and all SCP (12/12) participants (P = 0.2) transferred to an adult diabetes service; the median time to transfer was 14-15 wk. Overall, participants' frequency of adult diabetes service visits was sub-optimal but their retention in adult care was high. The only group difference was a higher HbA1c at baseline and follow-up in the CTP group. However, a general linear model found that follow-up HbA1c increased by 1.2% for each percentage increase in baseline HbA1c [95% confidence interval (0.4, 1.9; P = 0.01)], independent of treatment group.

CONCLUSIONS

Despite the challenges in recruiting adequate numbers, these findings provide valuable insights for future T1DM transition RCTs that are needed to build a more solid evidence-base in this field.

Population-based incidence of diabetes in Australian youth aged 10-18 yr: increase in type 1 diabetes but not type 2 diabetes

BACKGROUND

Global incidence of childhood type 2 diabetes has increased, with a greater rise amongst certain ethnic groups.

OBJECTIVES

To examine the change in the incidence of type 1 and type 2 diabetes in Australian youth, aged 10-18 yr, in New South Wales, Australia.

METHODS

Prospective population-based incidence study (2001-2008). Primary case ascertainment was from the Australasian Paediatric Endocrine Group Diabetes Register, secondary independent ascertainment from the National Diabetes Register.

RESULTS

There were 202 incident cases of type 2 diabetes (96 boys, 48%). The mean age at diagnosis (±SD) was 14.6 ± 2.5 yr; 93% were overweight (International Obesity Taskforce Grade ≥1). Mean HbA1c was 8.8 ± 2.8%. Ethnicity was Caucasian 31%, Indigenous Australian 20%, Southeast Asian 11%, North African/Middle Eastern 9%, and NewZealander/Melanesian/Polynesian 8%. The mean annual incidence of type 2 diabetes was 3.0 per 100 000 per year (95% confidence interval (CI): 2.6-3.4) and did not change over time. The mean annual incidence of type 1 diabetes was 22.0 per 100 000 per year (95% CI: 20.8-23.1), and increased by 3.8% per year [incidence rate ratio IRR: 1.04, 95% CI: 1.02-1.06, p = 0.001]. Incidence was higher in Indigenous vs. non-Indigenous youth, IRR: 6.9 (95% CI: 4.7-10.2, p < 0.001).

CONCLUSION

In 10-18 yr old youth, in Australia, the incidence of type 2 diabetes has remained steady during the last decade; however, the incidence of type 1 diabetes continues to rise. Most common diabetes in Australian youth is type 1 diabetes.

Improved insulin sensitivity and body composition, irrespective of macronutrient intake, after a 12 month intervention in adolescents with pre-diabetes; RESIST a randomised control trial

Background

A higher protein to carbohydrate ratio in the diet may potentiate weight loss, improve body composition and cardiometabolic risk, including glucose homeostasis in adults. The aim of this randomised control trial was to determine the efficacy of two structured lifestyle interventions, differing in dietary macronutrient content, on insulin sensitivity and body composition in adolescents. We hypothesised that a moderate-carbohydrate (40-45% of energy), increased-protein (25-30%) diet would be more effective than a high-carbohydrate diet (55-60%), moderate-protein (15%) diet in improving outcomes in obese, insulin resistant adolescents.

Methods

Obese 10–17 year olds with either pre-diabetes and/or clinical features of insulin resistance were recruited at two hospitals in Sydney, Australia. At baseline adolescents were prescribed metformin and randomised to one of two energy restricted diets. The intervention included regular contact with the dietician and a supervised physical activity program. Outcomes included insulin sensitivity index measured by an oral glucose tolerance test and body composition measured by dual-energy x-ray absorptiometry at 12 months.

Results

Of the 111 adolescents recruited, 85 (77%) completed the intervention. BMI expressed as a percentage of the 95th percentile decreased by 6.8% [95% CI: −8.8 to −4.9], ISI increased by 0.2 [95% CI: 0.06 to 0.39] and percent body fat decreased by 2.4% [95% CI: −3.4 to −1.3]. There were no significant differences in outcomes between diet groups at any time.

Conclusion

When treated with metformin and an exercise program, a structured, reduced energy diet, which is either high-carbohydrate or moderate-carbohydrate with increased-protein, can achieve clinically significant improvements in obese adolescents at risk of type 2 diabetes.

Trial registration

Australian New Zealand Clinical Trail Registry ACTRN12608000416392. Registered 25 August 2008.

Optimal macronutrient content of the diet for adolescents with prediabetes; RESIST a randomised control trial

CONTEXT

Prediabetes and clinical insulin resistance in adolescents are rapidly emerging clinical problems with serious health outcomes.

OBJECTIVE

The objective of this study was to determine the efficacy of 2 structured lifestyle interventions, both differing in diet macronutrient composition, on insulin sensitivity.

DESIGN

This study was a randomized controlled trial, known as Researching Effective Strategies to Improve Insulin Sensitivity in Children and Teenagers, in 2 hospitals in Sydney, Australia.

PARTICIPANTS

Participants included overweight or obese 10- to 17-year-olds with either prediabetes and/or clinical features of insulin resistance.

INTERVENTION

At baseline adolescents were prescribed metformin and randomized to a structured diet, which was either high carbohydrate or moderate carbohydrate with increased protein. The program commenced with a 3-month dietary intervention, with the addition of an exercise intervention in the next 3 months.

OUTCOMES

The outcomes included an insulin sensitivity, anthropometry, and cardiometabolic profile at 6 months.

RESULTS

One hundred eleven subjects (66 girls) were recruited and 98 subjects (58 girls) completed the 6-month intervention. After 3 months the mean insulin sensitivity index increased by 0.3 [95% confidence interval (CI) 0.2-0.4]. After 6 months the mean insulin (picomoles per liter) to glucose ratio (millimoles per liter) decreased by 7.2 [95%CI -12.0 to -2.3], body mass index, expressed as a percentage of the 95th centile, decreased by 9% (95% CI -3 to -15), but there was no significant change in the lipids. There were no significant differences in outcomes between the diet groups at any time point.

CONCLUSIONS

These results are in contrast with our hypothesis that adolescents randomized to the increased protein diet would have better outcomes. Further strategies are required to better address prediabetes and clinical features of insulin resistance in adolescents.

Home blood sodium monitoring, sliding-scale fluid prescription and subcutaneous DDAVP for infantile diabetes insipidus with impaired thirst mechanism

Background/Aims

Infants with diabetes insipidus (DI), especially those with impaired thirst mechanism or hypothalamic hyperphagia, are prone to severe sodium fluctuations, often requiring hospitalization. We aimed to avoid dangerous fluctuations in serum sodium and improve parental independence.

Methods

A 16-month old girl with central DI, absent thirst mechanism and hyperphagia following surgery for hypothalamic astrocytoma had erratic absorption of oral DDAVP during chemotherapy cycles. She required prolonged hospitalizations for hypernatremia and hyponatremic seizure. Intensive monitoring of fluid balance, weight and clinical assessment of hydration were not helpful in predicting serum sodium. Discharge home was deemed unsafe. Oral DDAVP was switched to subcutaneous (twice-daily injections, starting with 0.01mcg/dose, increasing to 0.024mcg/dose). The parents adjusted daily fluid allocation by sliding-scale, according to the blood sodium level (measured by handheld i-STAT analyser, Abbott). We adjusted the DDAVP dose if fluid allocation differed from maintenance requirements for 3 consecutive days.

Results

After 2.5 months, sodium was better controlled, with 84% of levels within reference range (135-145 mmol/L) vs. only 51% on the old regimen (p = 0.0001). The sodium ranged from 132-154 mmol/L, compared to 120–156 on the old regimen. She was discharged home.

Conclusion

This practical regimen improved sodium control, parental independence, and allowed discharge home.

Once daily insulin detemir in cystic fibrosis with insulin deficiency

The aim of this study was to determine if once daily insulin detemir reverses decline in weight and lung function in patients with cystic fibrosis (CF). 12 patients with early insulin deficiency and six with CF related diabetes (aged 7.2-18.1 years) were treated for a median of 0.8 years. Changes in weight and lung function following treatment were compared to pretreatment changes. Before treatment, the change in weight SD score (ΔWtSDS), percentage of predicted forced expiratory volume in 1 s (Δ%FEV(1)) and percentage of predicted forced vital capacity (Δ%FVC) declined in the whole study population (-0.45±0.38, -7.9±12.8%, -5.8±14.3%) and in the subgroup with early insulin deficiency (-0.41±0.43, -9.8±9.3%, -6.8±10.3%). Following treatment with insulin ΔWtSDS, Δ%FEV(1) and Δ%FVC significantly improved in the whole study population (+0.18±0.29 SDS, p=0.0001; +3.7±10.6%, p=0.007; +5.2±12.7%, p=0.013) and in patients with early insulin deficiency (+0.22±0.31 SDS, p=0.003; +5.3±11.5%, p=0.004; +5.8±13.4%, p=0.024). Randomised controlled trials are now needed.

Increased detection of cystic-fibrosis-related diabetes in Australia

OBJECTIVES

To estimate the incidence of cystic-fibrosis-related diabetes (CFRD) in youth from New South Wales (NSW) and the Australian Capital Territory (ACT), Australia and to examine demographic/clinical features at diagnosis.

METHODS

Incident cases of CFRD in young people aged ≤ 18 years diagnosed during 2000 to 2008 were identified from four paediatric cystic fibrosis (CF) clinics and the NSW/ACT Australasian Paediatric Endocrine Group Diabetes Register.

RESULTS

CFRD was diagnosed in 41 cases (59% girls). The estimated mean annual incidence of CFRD among patients with CF was 9.4 per 1000 person years (95% CI 6.8 to 12.8). Incidence increased from 2.0 per 1000 person years in 2000 to 22.1 per 1000 in 2008 (incidence RR 1.3, 95% CI 1.1 to 1.4). Haemoglobin A1c (HbA1c) was abnormal in the majority at diagnosis: median HbA1c was 6.9% (6.2-8.1%). More cases were diagnosed using an oral glucose tolerance test in 2007-2008 compared with previous years (61% vs 6%, p<0.001).

CONCLUSIONS

CFRD is increasingly recognised and now affects approximately one in five young people with CF. The rising incidence is likely to be due to increased detection, resulting from greater awareness and changes in screening practices. Widespread uptake of consensus guidelines for screening will ensure accurate case detection, but will also impact on patient care and resource allocation.

Persistently autoantibody negative (PAN) type 1 diabetes mellitus in children

BACKGROUND

Autoantibody-negative children diagnosed with type 1 diabetes might have unrecognized monogenic or type 2 diabetes.

RESEARCH DESIGN AND METHODS

At diagnosis of type 1 diabetes (between ages 0.5 and 16.3 yr, n = 470), autoantibodies [glutamic acid decarboxylase (GAD), insulinoma-associated protein 2 (IA2), insulin autoantibodies (IAA), and/or islet cell antibody (ICA)] were positive (ab+) in 330 and negative in 37 (unknown in 103). Autoantibody-negative patients were retested at median diabetes duration of 3.2 yr (range 0.9-16.2) for autoantibodies (GAD, IA2, ZnT8), human leukocyte antigen (HLA) typing, non-fasting C-peptide, and sequencing of HNF4A, HNF1A, KCNJ11, and INS.

RESULTS

Nineteen (5% of 367) remained persistently autoantibody negative (PAN), 17 were positive on repeat testing (PORT), and 1 refused retesting. No mutations were found in PORT. One PAN was heterozygous for P112L mutation in HNF1A and transferred from insulin to oral gliclazide. Another PAN transferred to metformin and the diagnosis was revised to type 2 diabetes. The remaining 17 PAN were indistinguishable from the ab+ group by clinical characteristics. HLA genotype was at high risk for type 1 diabetes in 82% of remaining PAN and 100% of PORT. After excluding patients with diabetes duration <1 yr, C-peptide was detectable more frequently in the remaining PAN (7/16) and PORT (6/17) than in a random selection of ab+ (3/28, p = 0.03).

CONCLUSIONS

The diagnosis of type 1 diabetes should be reevaluated in PAN patients, because a subset has monogenic or type 2 diabetes. The remaining PAN have relatively preserved C-peptide compared with ab+, suggesting slower β-cell destruction, but a very high frequency of diabetogenic HLA, implying that type 1B (idiopathic) diabetes is rare.

Bone mineral content and density in Rett syndrome and their contributing factors

This study used densitometry to investigate the areal bone mineral density (aBMD) and bone mineral content (BMC) in an Australian Rett syndrome cohort and to assess how factors such as genotype, epilepsy, BMI, and mobility affect these parameters. The influence of lean tissue mass (LTM) and bone area (BA) on total body BMC (TBBMC) was also investigated. Participants, recruited from the Australian Rett Syndrome Database (ARSD), had TBBMC and lumbar spine (LS) and femoral neck (FN) aBMD measured using Dual energy x-ray absorptiometry. Mean height standardized Z scores and CIs for the bone outcomes were obtained from multiple regression models. The mean height Z score for the FN aBMD was low at -2.20, while the LS aBMD was -0.72. The TBBMC mean height Z score was -0.62, although once adjusted for BA and LTM, the mean was above zero, suggesting that low BMC can be explained by narrow bones and decreased muscle mass, likely secondary to decreased mobility. Multiple linear regression identified the p.R168× and p.T158M mutations as the strongest predictors of low aBMC and BMD for all bone outcomes. The strong relationship between genotype, BMC, and aBMD is likely underpinned by the strong relationship between LTM, mobility, and bone outcome measures.

Vitamin D deficiency in children with inflammatory bowel disease

BACKGROUND

Osteopenia and osteoporosis are commonly seen in inflammatory bowel disease (IBD). Vitamin D deficiency potentially contributes to diminished bone acquisition in childhood.

OBJECTIVES

The objectives of this study were to assess vitamin D in a group of Australian children with IBD and to ascertain associations between vitamin D status and key clinical factors, for example disease location and severity.

METHODS

Data were obtained retrospectively from the records of children with IBD who had at least one measurement of serum 25-hydroxyvitamin D (25(OH)D) over a two-year period. Demographic variables, disease activity, inflammatory markers, disease location, duration, and therapy were recorded. Moderate and severe deficiency were defined as 25(OH)D <51 nmol/l and <30 nmol/l, respectively. Insufficiency was defined as 25(OH)D between 51 and 75 nmol/l.

RESULTS

Overall, the mean 25(OH)D level in 78 children (104 measurements) was 71.2 (SD ± 26.5) nmol/l. Fifteen (19%) children were vitamin D deficient and 30 (38%) children were insufficient. Levels of 25(OH)D were not associated with disease location or use of immunosuppressive drugs. Children with vitamin D deficiency had greater corticosteroid exposure than those with normal status (P = 0.001). The mean 25(OH)D of 38 children treated with nutritional therapy at diagnosis was higher than for 17 children initially treated with corticosteroids (P = 0.04).

CONCLUSIONS

A high proportion of these Australian children with IBD were vitamin D deficient. This emphasizes the importance of monitoring vitamin D status, and treating deficiency, in the management of pediatric IBD. The possible benefit of nutritional therapy in protection against vitamin D deficiency requires further prospective study.

Researching Effective Strategies to Improve Insulin Sensitivity in Children and Teenagers - RESIST. A randomised control trial investigating the effects of two different diets on insulin sensitivity in young people with insulin resistance and/or pre-diabetes

BACKGROUND

Concomitant with the rise in childhood obesity there has been a significant increase in the number of adolescents with clinical features of insulin resistance and prediabetes. Clinical insulin resistance and prediabetes are likely to progress to type 2 diabetes and early atherosclerosis if not targeted for early intervention. There are no efficacy trials of lifestyle intervention in this group to inform clinical practice. The primary aim of this randomised control trial (RCT) is to determine the efficacy and effectiveness of two different structured lifestyle interventions differing in diet composition on insulin sensitivity, in adolescents with clinical insulin resistance and/or prediabetes treated with metformin.

METHODS/DESIGN

This study protocol describes the design of an ongoing RCT. We are recruiting 108 (54 each treatment arm) 10 to 17 year olds with clinical features of insulin resistance and/or prediabetes, through physician referral, into a multi-centred RCT. All participants are prescribed metformin and participate in a diet and exercise program. The lifestyle program is the same for all participants except for diet composition. The diets are a high carbohydrate, low fat diet and a moderate carbohydrate, increased protein diet.The program commences with an intensive 3 month dietary intervention, implemented by trained dietitians, followed by a 3 month intensive gym and home based exercise program, supervised by certified physical trainers. To measure the longer term effectiveness, after the intensive intervention trial participants are managed by either their usual physician or study physician and followed up by the study dietitians for an additional 6 months. The primary outcome measure, change in insulin sensitivity, is measured at 3, 6 and 12 months.

DISCUSSION

Clinical insulin resistance and prediabetes in the paediatric population are rapidly emerging clinical problems with serious health outcomes. With appropriate management these conditions are potentially reversible or at least their progression can be delayed. This research study is the first trial designed to provide much needed data on the effective dietary management for this cohort. This study will inform clinical practice guidelines for adolescents with clinical insulin resistance and may assist in preventing metabolic complications, type 2 diabetes and early cardiovascular disease.

TRIAL REGISTRATION

Australian and New Zealand Clinical Trials Registration Number ACTRN12608000416392.

Effect of exclusive enteral nutrition on bone turnover in children with Crohn's disease

BACKGROUND

Poor bone acquisition and increased fracture risk are significant complications associated with Crohn's disease (CD). The aim of this study was to determine the effects of 8 weeks of exclusive enteral nutrition (EEN) therapy upon markers of bone turnover in children with newly diagnosed CD.

METHODS

Twenty-three children with newly diagnosed CD and 20 controls (without CD) were enrolled. Children with CD were treated with 8 weeks of EEN. Inflammatory markers [C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), albumin, platelets], nutritional markers (height, weight), and bone markers [C-terminal telopeptides of Type-1 collagen (CTX) and bone specific alkaline phosphatase (BAP)] were measured prior to and following therapy.

RESULTS

At diagnosis, children with CD had elevated serum CTX (2.967 +/- 0.881 ng/ml) compared to controls (2.059 +/- 0.568 ng/ml; P = 0.0003). Following the period of EEN, CTX levels fell significantly (2.260 +/- 0.547 ng/ml; P = 0.002), while serum BAP levels (51.24 +/- 31.31 microg/L at diagnosis; control serum BAP = 66.80 +/- 23.23 microg/L; P = 0.07) increased significantly (64.82 +/- 30.51 microg/L; P = 0.02), with both normalizing to control levels.

CONCLUSIONS

As well as reducing inflammation, decreasing disease activity, and improving nutrition in children with newly diagnosed CD, EEN therapy also normalized serum markers of bone turnover, suggesting an improvement in bone health. Further investigations of short- and long-term effects of EEN on bone density and overall bone health are now required.

Diagnosis and management of childhood obesity: a survey of general practitioners in South West Sydney

AIM

To describe general practitioners' (GPs) diagnosis and management of overweight and obesity in children, their attitudes regarding obesity and their awareness of National Health and Medical Research Council (NHMRC) clinical practice guidelines.

METHOD

A cross-sectional written survey of members of the Liverpool Division of General Practice (located in South West Sydney, Australia).

RESULTS

Of 137 questionnaires sent, 85 (62%) were returned. Although the majority prescribed the correct interventions, there was variability in complications screening, ranging from 75% screening for psychosocial problems to 30% for fatty liver. Less than a third (28%) of GPs used NHMRC guidelines in their practice and only 9% used body mass index charts to correctly diagnose childhood obesity. GPs felt that childhood obesity was a significant issue and identified parental denial and lack of community support as barriers to treatment.

CONCLUSION

Although NHMRC guideline adherence was far from universal, the GPs in our survey are motivated and aware of the importance of managing childhood obesity. If the primary care approach is to work, then GPs need support and education in an environment where there is greater community awareness of the impact of childhood obesity.

Insulin allergy desensitization with simultaneous intravenous insulin and continuous subcutaneous insulin infusion

Persistent 'IgE-mediated' insulin allergy (type 1 allergy) (1), unresponsive to changes in insulin type or the use of antihistamines, necessitates desensitization. A number of case reports (2-7) and recent reviews (8, 9) have demonstrated that desensitization can be achieved with continuous subcutaneous insulin infusion (CSII), but in type 1 diabetes mellitus, the need to slowly increase insulin dose from sub-therapeutic levels competes with the need for glycaemic control and suppression of ketogenesis. Tolerance to intravenous (IV) insulin despite persistent life-threatening allergic reactions to subcutaneous human insulin (bolus or CSII) has been recently described (10). We present the cases of two unrelated 9-yr-old boys with persistent generalized urticarial reactions to subcutaneous injections of all available insulin types, despite treatment with oral antihistamines. After failed rapid desensitization to insulin delivered by either subcutaneous injection or CSII, the concurrent use of IV insulin allowed desensitization to CSII over 5-6 d.

Sex-specific developmental changes in muscle size and bone geometry at the femoral shaft

INTRODUCTION

When expressed as a percentage of the average result in young adults, bone mineral content lags behind bone length before puberty. Even though this observation has led to speculation about bone fragility in children, such relationships could simply be due to scaling effects when measures with different geometrical dimensions are compared.

METHODS

The study population comprised 145 healthy subjects (6-25 years, 94 females). Magnetic resonance imaging and dual-energy X-ray absorptiometry were used to determine femur length, bone mineral content, cortical bone mineral density, cross-sectional bone geometry (bone diameter; cortical thickness; total, cortical and medullary areas; cross-sectional and polar moments of area; bone strength index) and muscle area at the proximal one-third site of the femur. Results were dimensionally scaled by raising two-, three- and four-dimensional variables to the power of 1/2, 1/3 and 1/4, respectively. Sex-differences were also assessed before and after functionally adjusting variables for femur length and weight or muscle size.

RESULTS

In prepubertal children, unscaled results expressed as percentages of adult values were lowest for variables with the highest dimensions (e.g., moments of area<bone mineral content<cross-sectional areas<femur length). However, when dimensionally scaled, results in children represented similar percentages of the respective average adult values, even after functional adjustments. Before puberty, there was no sex-difference in adjusted bone or muscle variables. After puberty, males had greater total and cortical bone area, bone diameter, moments of area, bone strength index and muscle area than women, both in absolute terms as well as adjusted for femur length and weight. The largest sex-difference was found for muscle area. When compared relative to muscle size, young adult women attained greater total and cortical bone area than men.

CONCLUSIONS

Growth in femoral length, diameter, mass and strength appears well coordinated before puberty. Postpubertal females have narrower femora, less bone strength and muscle size than males. However, when muscle size is taken into account, females have a larger femoral bone cross-section and more cortical bone. These sex-differences likely result from a combination of mechanical and hormonal effects occurring during puberty.

The re-emerging burden of rickets: a decade of experience from Sydney

AIM

To define the demographics and clinical characteristics of cases presenting with nutritional rickets to paediatric centres in Sydney, Australia.

METHODS

Retrospective descriptive study of 126 cases seen from 1993 to 2003 with a diagnosis of vitamin D deficiency and/or confirmed rickets defined by long bone x ray changes.

RESULTS

A steady increase was seen in the number of cases per year, with a doubling of cases from 2002 to 2003. Median age of presentation was 15.1 months, with 25% presenting at less than 6 months of age. The most common presenting features were hypocalcaemic seizures (33%) and bowed legs (22%). Males presented at a younger age, with a lower weight SDS, and more often with seizures. The caseload was almost exclusively from recently immigrated children or first generation offspring of immigrant parents, with the region of origin predominantly the Indian subcontinent (37%), Africa (33%), and the Middle East (11%). Seventy nine per cent of the cases were born in Australia. Eleven cases (all aged <7 months) presented atypically with hyperphosphataemia.

CONCLUSIONS

This large case series shows that a significant and increasing caseload of vitamin D deficiency remains, even in a developed country with high sunlight hours. Cases mirror recent immigration trends. Since birth or residence in Australia does not appear to be protective, screening of at risk immigrant families should be implemented through public health policies.

Cyclic bisphosphonate therapy in osteogenesis imperfecta type V

The clinical and radiographic features and management of a young person with recently delineated Osteogenesis Imperfecta Type V is described. A female aged 9 years presented with a history of multiple fractures since 3 years of age and bilateral dislocation of the elbows from infancy. She was commenced on a low dose frequent regimen of cyclic intravenous pamidronate, which resulted in progressive improvement in bone density, reduced fracture frequency and remission of symptoms of osteoporosis.

A comparison of bone geometry and cortical density at the mid-femur between prepuberty and young adulthood using magnetic resonance imaging

In upper extremity bones, a sexual dimorphism exists in the development of periosteal and endocortical bone surfaces during growth. Little is known about developmental patterns of bone geometry at weight-bearing bones like the femur. Using MRI and dual energy X-ray absorptiometry (DXA), this study assessed the differences in mid-femoral total (TA), cortical (CA) and medullary areas (MA), cortical thickness, and cortical density (BMD(compartment)) between prepuberty and young adulthood in 145 healthy subjects (94 females) 6 to 25 years old. Additionally, agreement between mid-femoral total bone volume (TV) measurements by DXA and MRI were investigated. In both sexes, TA, CA, MA, and cortical thickness were significantly larger in adults compared to prepubertal subjects (P < 0.001), and males had greater values than females. This sex difference persisted for TA, CA, and cortical thickness (P < 0.05), but not MA, after adjusting for femur length and weight. Mean (SD) cortical BMD increased from 1.05 (0.07) and 1.09 (0.10) g/cm(3) in prepubertal children to 1.46 (0.14) and 1.42 (0.1) g/cm(3) in young adults, females and males, respectively (P < 0.001). TV measurements by DXA were significantly greater than by MRI (P < 0.001) in young adults. In conclusion, periosteal and endocortical expansion and increasing cortical BMD are the growth processes found at the mid-femur in both sexes. Our findings contrast to that in upper extremity bones, where MA is constant in females during growth. The difference in femoral bone development may be due to higher strains caused by weight bearing and genetic factors. DXA, in contrast to MRI, is inaccurate in the determination of mid-femoral TV measures.

Importance of lean mass in the interpretation of total body densitometry in children and adolescents

OBJECTIVE

Most studies that use total body dual energy x-ray absorptiometry (DEXA) in children rely on areal bone mineral density (BMD=bone mineral content [BMC]/bone area [BA]) and compare the output with age- and sex-specific normative data. Because this approach is prone to size-related misinterpretation, this study focuses on the interrelations among BMC, body size (height), and lean tissue mass (LTM).

STUDY DESIGN

This cross-sectional study presents normative total body LTM data in relation to height and BMC for 459 healthy white subjects (249 female), 3 to 30 years of age. Guidelines for DEXA interpretation in children are provided and illustrated for patients with growth hormone deficiency (n=5) and anorexia nervosa (n=5).

RESULTS

LTM/height tended to be greater in male than in girls. The BMC/LTM ratio was greater in female than in boys (P<.001), even after adjustment for age and height. Sex-specific reference curves were created for LTM/height, the BMC/LTM ratio, BA/height, and BMC/BA.

CONCLUSIONS

We recommend that total body DEXA in children should be interpreted in 4 steps: (1) BMD or BMC/age, (2) height/age, (3) LTM/height, and (4) BMC/LTM ratio for height. This allows differentiation of the origin of a low BMD or BMC/age, for example, short stature and primary, secondary, and mixed bone defects.

Measurement of midfemoral shaft geometry: repeatability and accuracy using magnetic resonance imaging and dual-energy X-ray absorptiometry

Although macroscopic geometric architecture is an important determinant of bone strength, there is limited published information relating to the validation of the techniques used in its measurement. This study describes new techniques for assessing geometry at the midfemur using magnetic resonance imaging (MRI) and dual-energy X-ray absorptiometry (DXA) and examines both the repeatability and the accuracy of these and previously described DXA methods. Contiguous transverse MRI (Philips 1.5T) scans of the middle one-third femur were made in 13 subjects, 3 subjects with osteoporosis. Midpoint values for total width (TW), cortical width (CW), total cross-sectional area (TCSA), cortical cross-sectional area (CCSA), and volumes from reconstructed three-dimensional (3D) images (total volume [TV] and cortical volume [CVol]) were derived. Midpoint TW and CW also were determined using DXA (Lunar V3.6, lumbar software) by visual and automated edge detection analysis. Repeatability was assessed on scans made on two occasions and then analyzed twice by two independent observers (blinded), with intra- and interobserver repeatability expressed as the CV (CV +/- SD). Accuracy was examined by comparing MRI and DXA measurements of venison bone (and Perspex phantom for MRI), against "gold standard" measures made by vernier caliper (width), photographic image digitization (area) and water displacement (volume). Agreement between methods was analyzed using mean differences (MD +/- SD%). MRI CVs ranged from 0.5 +/- 0.5% (TV) to 3.1 +/- 3.1% (CW) for intraobserver and 0.55 +/- 0.5% (TV) to 3.6 +/- 3.6% (CW) for interobserver repeatability. DXA results ranged from 1.6 +/- 1.5% (TW) to 4.4 +/- 4.5% (CW) for intraobserver and 3.8 +/- 3.8% (TW) to 8.3 +/- 8.1% (CW) for interobserver variation. MRI accuracy was excellent for TV (3.3 +/- 6.4%), CVol (3.5 +/- 4.0%), TCSA (1.8 +/- 2.6%), and CCSA (1.6 +/- 4.2%) but not TW (4.1 +/- 1.4%) or CW (16.4 +/14.9%). DXA results were TW (6.8 +/- 2.7%) and CW (16.4 +/- 17.0%). MRI measures of geometric parameters of the midfemur are highly accurate and repeatable, even in osteoporosis. Both MRI and DXA techniques have limited value in determining cortical width. MRI may prove valuable in the assessment of surface-specific bone accrual and resorption responses to disease, therapy, and variations in mechanical loading.

Bone markers and bone mineral density during growth hormone treatment in children with growth hormone deficiency

Growth hormone (GH) has a positive impact on muscle mass, growth and bone formation. It is known to interact with the bone-forming unit, with well-documented increases in markers of bone formation and bone resorption within weeks of the start of GH therapy. These changes relate significantly to short-term growth rate, but it is not evident that they predict long-term response to GH therapy. The consequences of GH deficiency (GHD) and GH replacement therapy on bone mineral density (BMD) have been difficult to interpret in children because of the dependency of areal BMD on height and weight. Some studies have tried to overcome this problem by calculating volumetric BMD, but results are conflicting. The attainment of a normal peak bone mass in an individual is considered important for the future prevention of osteoporosis. From the limited data available, it appears difficult to normalize bone mass totally in GH-deficient individuals, despite GH treatment for long periods. Studies to date examining the interaction between GH and bone have included only small numbers of individuals, making it difficult to interpret the study findings. It is hoped that these issues can be clarified in future research by the direct measurement of bone density (using quantitative computer tomography). Mineralization is only one facet of bone strength, however; other important components (e.g. bone structure and geometry) should be addressed in future paediatric studies. Future studies could also address the importance of the degree of GHD in childhood; how GH dose and insulin-like growth factor-I levels achieved during therapy relate to the final outcome; whether or not the continuation of GH therapy after the attainment of final height may further enhance bone mass; whether the timing and dose of other treatments (e.g. sex hormone replacement therapy) are critical to the outcome; and whether GHD in childhood is associated with an increased risk of fracture.