Heidi J. Kalkwarf

Official Positions of the International Society for Clinical Densitometry and executive summary of the 2007 ISCD Pediatric Position Development Conference.

The International Society for Clinical Densitometry (ISCD) convenes a Position Development Conference (PDC) every 2 yr to make recommendations for standards in the field of bone densitometry. The recommendations are based on clinically relevant issues in bone densitometry such as quality control, acquisition, analysis, interpretation, and reporting. In 2007, ISCD convened its first Pediatric Position Development Conference to address issues specific to the assessment of skeletal health in children and adolescents. Topics for consideration are developed by the ISCD Board of Directors and its Scientific Advisory Committee. Clinically relevant questions related to each topic area are assigned to task forces for a comprehensive review of the medical literature and subsequent presentation of the reports to an international panel of experts. For this PDC, the Expert Panel included representatives of the American Society for Bone and Mineral Research and International Bone and Mineral Society. The recommendations of the PDC Expert Panel are then reviewed by the ISCD Board of Directors. Recommendations that are approved become Official Positions of the ISCD. The Pediatric PDC was held June 20-21, 2007, in Montreal, Quebec, Canada. Topics considered were restricted to children and adolescents, and included DXA prediction of fracture and definition of osteoporosis; DXA assessment in diseases that may affect the skeleton; DXA interpretation and reporting; and peripheral quantitative computed tomography measurement. This report describes the methodology and results of the 2007 Pediatric PDC, and a summary of all ISCD Official Positions, including the ones recently adopted by this 2007 Pediatric PDC and the 2007 Lansdowne, Virginia, USA Adult PDC.

International Society for Clinical Densitometry 2007 Adult and Pediatric Official Positions

The International Society for Clinical Densitometry (ISCD) periodically convenes Position Development Conferences (PDCs) in order to establish standards and guidelines for the assessment of skeletal health. The most recent Adult PDC was held July 20-22, 2007, in Lansdowne, Virginia, USA; the first Pediatric PDC was June 20-21, 2007 in Montreal, Quebec, Canada. PDC topics were selected according to clinical relevancy, perceived need for standardization, and likelihood of achieving agreement. Each topic area was assigned to a task force for a comprehensive review of the scientific literature. The findings of the review and recommendations were presented to adult and pediatric international panels of experts. The panels voted on the appropriateness, necessity, quality of the evidence, strength, and applicability (worldwide or variable according to local requirements) of each recommendation. Those recommendations that were approved by the ISCD Board of Directors become Official Positions. This is a review of the methodology of the PDCs and selected ISCD Official Positions.

THE EFFECT OF CALCIUM SUPPLEMENTATION ON BONE DENSITY DURING LACTATION AND AFTER WEANING

BACKGROUND Women may lose bone during lactation because of calcium lost in breast milk. We studied whether calcium supplementation prevents bone loss during lactation or augments bone gain after weaning. METHODS We conducted two randomized, placebo-controlled trials of calcium supplementation (1 g per day) in postpartum women. In one trial (the study of lactation), 97 lactating and 99 nonlactating women were enrolled a mean (+/-SD) of 16+/-2 days post partum. In the second trial (the study of weaning), 95 lactating women who weaned their infants in the 2 months after enrollment and 92 nonlactating women were enrolled 5.6+/-0.8 months post partum. The bone density of the total body, lumbar spine, and forearm was measured at enrollment and after three and six months. RESULTS The bone density of the lumbar spine decreased by 4.2 percent in the lactating women receiving calcium and by 4.9 percent in those receiving placebo and increased by 2.2 and 0.4 percent, respectively, in the nonlactating women (P<0.001 for the effect of lactation; P= 0.01 for the effect of calcium). After weaning, the bone density of the lumbar spine increased by 5.9 percent in the lactating women receiving calcium and by 4.4 percent in those receiving placebo; it increased by 2.5 and 1.6 percent, respectively, in the nonlactating women (P<0.001 for the effects of lactation and calcium). There was no effect of either lactation or calcium supplementation on bone density in the forearm, and there was no effect of calcium supplementation on the calcium concentration in breast milk. CONCLUSIONS Calcium supplementation does not prevent bone loss during lactation and only slightly enhances the gain in bone density after weaning.

Height Adjustment in Assessing Dual Energy X- Ray Absorptiometry Measurements of Bone Mass and Density in Children

CONTEXT In children, bone mineral content (BMC) and bone mineral density (BMD) measurements by dual-energy x-ray absorptiometry (DXA) are affected by height status. No consensus exists on how to adjust BMC or BMD (BMC/BMD) measurements for short or tall stature. OBJECTIVE The aim of this study was to compare various methods to adjust BMC/BMD for height in healthy children. DESIGN Data from the Bone Mineral Density in Childhood Study (BMDCS) were used to develop adjustment methods that were validated using an independent cross-sectional sample of healthy children from the Reference Data Project (RDP). SETTING We conducted the study in five clinical centers in the United States. PARTICIPANTS We included 1546 BMDCS and 650 RDP participants (7 to 17 yr of age, 50% female). INTERVENTION No interventions were used. MAIN OUTCOME MEASURES We measured spine and whole body (WB) BMC and BMD Z-scores for age (BMC/BMD(age)), height age (BMC/BMD(height age)), height (BMC(height)), bone mineral apparent density (BMAD(age)), and height-for-age Z-score (HAZ) (BMC/BMD(haz)). RESULTS Spine and WB BMC/BMD(age)Z and BMAD(age)Z were positively (P < 0.005; r = 0.11 to 0.64) associated with HAZ. Spine BMD(haz) and BMC(haz)Z were not associated with HAZ; WB BMC(haz)Z was modestly associated with HAZ (r = 0.14; P = 0.0003). All other adjustment methods were negatively associated with HAZ (P < 0.005; r = -0.20 to -0.34). The deviation between adjusted and BMC/BMD(age) Z-scores was associated with age for most measures (P < 0.005) except for BMC/BMD(haz). CONCLUSIONS Most methods to adjust BMC/BMD Z-scores for height were biased by age and/or HAZ. Adjustments using HAZ were least biased relative to HAZ and age and can be used to evaluate the effect of short or tall stature on BMC/BMD Z-scores.

Revised Reference Curves for Bone Mineral Content and Areal Bone Mineral Density According to Age and Sex for Black and Non-Black Children: Results of the Bone Mineral Density in Childhood Study

CONTEXT Deficits in bone acquisition during growth may increase fracture risk. Assessment of bone health during childhood requires appropriate reference values relative to age, sex, and population ancestry to identify bone deficits. OBJECTIVE The objective of this study was to provide revised and extended reference curves for bone mineral content (BMC) and areal bone mineral density (aBMD) in children. DESIGN The Bone Mineral Density in Childhood Study was a multicenter longitudinal study with annual assessments for up to 7 yr. SETTING The study was conducted at five clinical centers in the United States. PARTICIPANTS Two thousand fourteen healthy children (992 males, 22% African-Americans) aged 5-23 yr participated in the study. INTERVENTION There were no interventions. MAIN OUTCOME MEASURES Reference percentiles for BMC and aBMD of the total body, lumbar spine, hip, and forearm were obtained using dual-energy x-ray absorptiometry for Black and non-Black children. Adjustment factors for height status were also calculated. RESULTS Extended reference curves for BMC and aBMD of the total body, total body less head, lumbar spine, total hip, femoral neck, and forearm for ages 5-20 yr were constructed relative to sex and age for Black and non-Black children. Curves are similar to those previously published for 7-17 year olds. BMC and aBMD values were greater for Black vs. non-Black children at all measurement sites. CONCLUSIONS We provide here dual-energy x-ray absorptiometry reference data on a well-characterized cohort of 2012 children and adolescents. These reference curves provide the most robust reference values for the assessment and monitoring of bone health in children and adolescents in the literature to date.

Bone mineral loss during lactation and recovery after weaning.

Objective To test the hypothesis that bone mineral content (BMC) and density (BMD) are lost during lactation and regained within 6 months after weaning. Methods Two cohorts of women, defined by time postpartum, were enrolled into the study; each cohort was followed for 6 months. Women in the lactation cohort (65 lactating women and 48 nonlactating postpartum controls) were enrolled at 2 weeks postpartum. Women in the weaning cohort (40 lactating and 43 nonlactating postpartum controls) were enrolled at 4–6 months postpartum. Lactating women enrolled in the weaning cohort had been fully breast-feeding at enrollment and weaned within 2 months of enrollment. Bone mineral content of the total body and BMD of the lumbar spine and distal radius were measured by dualenergy x-ray absorptiometry. Results Lactating women lost significantly more bone in the total body (−2.8 versus −1.7%) and lumbar spine (−3.9 versus 1.5%) than did nonlactating women during the first 6 months postpartum. There was no effect of lactation on bone changes at the distal radius. After weaning, lactating women gained significantly more bone in the lumbar spine than did nonlactating women (5.5 versus 1.8%). Earlier resumption of menses was associated with a smaller loss of bone during lactation and a greater increase of bone after weaning. Conclusion Women lose bone during lactation but gain bone after weaning. Thus, lactation may not result in net bone loss.

Bone mineral changes during pregnancy and lactation

Significant calcium transfer from the mother to the fetus and infant occurs during pregnancy and lactation, theoretically placing the mother at an increased risk for osteoporosis later in life. During pregnancy, intestinal calcium absorption increases to meet much of the fetal calcium needs. Maternal bone loss also may occur in the last months of pregnancy, a time when the fetal skeleton is rapidly mineralizing. The calcium needed for breast milk production is met through renal calcium conservation and, to a greater extent, by mobilization of calcium from the maternal skeleton. Women experience a transient loss of approx 3–7% of their bone density during lactation, which is rapidly regained after weaning. The rate and extent of recovery are influenced by the duration of lactation and postpartum amenorrhea and differ by skeletal site. Additional calcium intake does not prevent bone loss during lactation or enhance the recovery after weaning. The recovery of bone is complete for most women and occurs even with shortly spaced pregnancies. Epidemiologic studies have found that pregnancy and lactation are not associated with an increased risk of osteoporotic fractures.

Lower weight-for-age z score adversely affects hospital length of stay after the bidirectional Glenn procedure in 100 infants with a single ventricle

OBJECTIVE Poor growth has been described in infants with a single ventricle; however, little is known regarding its effect on surgical outcomes. We sought to assess the effect of nutritional status at the time of the bidirectional Glenn procedure on short-term outcomes. METHODS We performed a retrospective case series of children who underwent the bidirectional Glenn procedure at our institution between January 2001 and December 2007. Anthropometric measurements were recorded at the time of neonatal admission and the bidirectional Glenn procedure. Data from preoperative echocardiograms and cardiac catheterization were recorded. The primary outcome variable was length of hospital stay. RESULTS Data on 100 infants were included for analysis. Age at the time of the bidirectional Glenn procedure was 5.1 months (range, 2.4-10 months). The median weight-for-age z score at birth was -0.4 (range, -2.6 to 3.2), and by the time of the bidirectional Glenn procedure, it had decreased to -1.3 (range, -3.9 to 0.6). In multivariable modeling longer postoperative hospital stays were predicted by lower weight-for-age z score (P = .02), younger age (P < .001), being fed through a gastrostomy tube (P = .01), and undergoing concomitant aortic arch reconstruction (P < .001) at the time of the bidirectional Glenn procedure. CONCLUSIONS There is suboptimal weight gain between neonatal discharge and the bidirectional Glenn procedure. A lower weight-for-age z score and younger age at the time of the bidirectional Glenn procedure affects length of hospital stay independent of hemodynamic or echocardiographic variables.

Dietary patterns associated with fat and bone mass in young children

BACKGROUND Obesity and osteoporosis have origins in childhood, and both are affected by dietary intake and physical activity. However, there is little information on what constitutes a diet that simultaneously promotes low fat mass and high bone mass accrual early in life. OBJECTIVE Our objective was to identify dietary patterns related to fat and bone mass in children during the age period of 3.8-7.8 y. DESIGN A total of 325 children contributed data from 13 visits over 4 separate study years (age ranges: 3.8-4.8, >4.8-5.8, >5.8-6.8, and >6.8-7.8 y). We performed reduced-rank regression to identify dietary patterns related to fat mass and bone mass measured by dual-energy X-ray absorptiometry for each study year. Covariables included race, sex, height, weight, energy intake, calcium intake, physical activity measured by accelerometry, and time spent viewing television and playing outdoors. RESULTS A dietary pattern characterized by a high intake of dark-green and deep-yellow vegetables was related to low fat mass and high bone mass; high processed-meat intake was related to high bone mass; and high fried-food intake was related to high fat mass. Dietary pattern scores remained related to fat mass and bone mass after all covariables were controlled for (P < 0.001-0.03). CONCLUSION Beginning at preschool age, diets rich in dark-green and deep-yellow vegetables and low in fried foods may lead to healthy fat and bone mass accrual in young children.

Special report on the 2007 adult and pediatric Position Development Conferences of the International Society for Clinical Densitometry.

The International Society for Clinical Densitometry (ISCD) conducts Position Development Conferences (PDCs) for the purpose of establishing standards and guidelines in the field of bone densitometry. Topics for consideration are selected according to clinical relevance, a perceived need for standardization, and the likelihood of achieving agreement. Questions regarding nomenclature, indications, acquisition, analysis, quality control, interpretation, and reporting of bone density tests for each topic area are assigned to task forces for a comprehensive review of the scientific literature. The findings of the review and recommendations are then presented to an international panel of experts at the PDC. The expert panel votes on potential Official Positions for appropriateness, necessity, quality of the evidence, strength of the recommendation, and applicability (worldwide or variable according to local requirements). Recommendations that are approved by the ISCD Board of Directors become Official Positions. The first Pediatric PDC was 20–21 June 2007 in Montreal, QC, Canada. The most recent Adult PDC was held 20–22 July 2007, in Lansdowne, VA, USA. This Special Report summarizes the methodology of the ISCD PDCs and presents selected Official Positions of general interest.