Bone densitometry in infants and young children: the 2013 ISCD Pediatric Official Positions.

Infants and children <5 yr were not included in the 2007 International Society for Clinical Densitometry Official Positions regarding Skeletal Health Assessment of Children and Adolescents. To advance clinical care of very young children, the International Society for Clinical Densitometry 2013 Position Development Conference reviewed the literature addressing appropriate methods and skeletal sites for clinical dual-energy X-ray absorptiometry (DXA) measurements in infants and young children and how results should be reported. DXA whole-body bone mineral content and bone mineral density for children ≥3 yr and DXA lumbar spine measurements for infants and young children 0-5 yr were identified as feasible and reproducible. There was insufficient information regarding methodology, reproducibility, and reference data to recommended forearm and femur measurements at this time. Appropriate methods to account for growth delay when interpreting DXA results for children <5 yr are currently unknown. Reference data for children 0-5 yr at multiple skeletal sites are insufficient and are needed to enable interpretation of DXA measurements. Given the current scarcity of evidence in many areas, it is likely that these positions will change over time as new data become available.

Bone ultrasound velocity in neonates with intrauterine growth deficit reflects a growth continuum.

Both bone mass by densitometry and speed of sound (SOS) from quantitative ultrasound of the bone (QUS) are directly related to bone strength. However, reports of lower bone mass but higher SOS in neonates with intrauterine growth deficit lead to apparent contradictory conclusions on bone strength. Three groups of infants were studied: small for gestation (SGA) with birth weights ≤10th percentile for gestation and 2 control groups with appropriate birth weights (11th to 90th percentile) for gestation (AGA): matched to SGA group for gestation and birth weight, respectively. SOS was measured with a commercial QUS instrument (Sunlight Omnisense 7000, Sunlight Medical Ltd, Tel Aviv, Israel) and 2 manufacturer supplied ultrasound probes (CS and CR) for small bones. The SGA group had significantly (p<0.01) higher SOS compared with weight matched but gestational less matured control group by an average of 54m/s with the CS probe and 80m/s with the CR probe but not significantly different from gestation-matched AGA group. SOS values from both probes were significantly correlated (r=0.71-0.91) but were significantly different between probes. Probe failure occurred with both probes. We conclude that QUS SOS values in SGA neonates are a reflection of a continuum of intrauterine maturation of the skeleton.

Developmental variations in plasma leptin, leptin soluble receptor and their molar ratio in healthy infants.

BACKGROUND: Leptin and its soluble receptor (sOB-R) are important to regulation of body composition but there are no data on the developmental variations in these plasma variables and their relationship with body composition measurements, METHODS: Weight, length, and body composition (bone, fat and lean mass) by dual energy absorptiometry, and plasma variables were measured in healthy infants at 2, 4, 8 and 12 months. RESULTS: 15 whites and 29 African Americans (21 males and 23 females) with mean birth weight 3357 +/- 45 (SEM) g and gestation of 39.3 +/- 0.17 weeks were studied. The overall Z score for weight, length and weight for length during the study were 0.00 +/- 0.15, -0.08 +/- 0.11 and 0.12 +/- 0.14 respectively. With increasing age, plasma leptin (1.0 to 18.2, median 5.5 ng/mL) and sOB-R:leptin molar ratio (10.1 to 247.4, median 59.9) were lowered (r = -0.47, p < 0.01; and r = -0.37, p < 0.05 respectively), best predicted by weight Z score and percentage of fat mass, and higher in African American and female. Presence of body composition measurements eliminated the race and gender effect on the plasma variables. Plasma sOB-R (49.5 to 173.9, median 81.3 ng/mL) did not change significantly with age and was correlated and predicted only by body composition measurements. CONCLUSION: In healthy growing infants, plasma leptin but not sOB-R decreases with age. Gender, race and anthropometric measurements are additional physiological determinants predictive of plasma leptin and the receptor:ligand ratio. However, body composition is the only variable that can predict plasma leptin and its soluble receptor and the receptor: ligand ratio; and body composition measurements eliminated the race and gender effect on these plasma variables.

Posthospital discharge feeding for preterm infants: effects of standard compared with enriched milk formula on growth, bone mass, and body composition.

BACKGROUND: Despite the theoretical benefits of nutrient-enriched formula given to preterm infants after hospital discharge, its role in reversing growth deficits after hospital discharge remains poorly defined. OBJECTIVE: The aim was to determine the effect of different formulas on the growth, bone mass, and body composition of preterm infants after hospital discharge. DESIGN: This was a randomized, double blind comparison of a nutrient-enriched formula (EF) and a formula for term infants (TF) given for 1 y after hospital discharge. Compared with the TF, the EF had a higher energy density and higher contents of protein, calcium, and phosphorus (by 10%, 21%, 44%, and 11%, respectively) and higher contents of almost all other nutrients (by >or=10%). RESULTS: Birth weights of the infants were 630-1620 g (median: 1250 g) and gestational ages were 24-34 wk (median: 29 wk). TF resulted in significantly greater weight, length, head circumference measurements, and their respective z scores on the basis of age- and sex-specific norms. At the end of the study, the mean z scores for the corrected age of infants in the TF group were -0.37 for weight, 0.001 for length, and 0.50 for head circumference. The TF group also had significantly greater dual-energy X-ray absorptiometry measured bone and lean and fat mass than did the EF group (P < 0.05 for all comparisons). CONCLUSIONS: The use of EF for preterm infants after hospital discharge shows no advantage over TF in growth, bone mineralization, and body composition. More studies are needed to determine the optimal postdischarge nutrition support for preterm infants.

Anthropometric status in Palestinian children living in refugee camps in Lebanon.

OBJECTIVE: To study the relationship between anthropometric measurements and living conditions in infants and children living in refugee camps. DESIGN: Cross-sectional study. SETTING: Four Palestinian refugee camps in Lebanon. SUBJECTS: Thirty-three infants younger than two years of age and 234 children (106 males) younger than 15 years of age. METHODS: Weight and height were measured. Body mass index (BMI) was calculated as weight (kg)/length squared (m2). A parent of the subject answered a questionnaire on employment status, household size, food, and financial assistance as well as child's food consumption. RESULTS: Anthropometric measurements were standardized to the National Center of Health Statistics (NCHS) growth data as age- and sex-specific Z scores. No significant difference was seen between males and females. For all sites studied, the Z scores for weight (WAZ) and height (HAZ) of infants were not significantly different from zero. Among older children, WAZ, HAZ, and Z scores for BMI (BMIZ) were significantly less than zero. In infants, exclusive breast feeding, in addition to receiving financial help, correlated positively while meat and fruit consumption of less than three times per week correlated negatively with WAZ and HAZ. In older children, a mixed relationship was seen among the number of children younger than 10 years of age in a household, the child's meat, vegetable, and fruit consumption less than three times per week, and WAZ and HAZ. CONCLUSION: Living conditions and socioeconomic restrictions on Palestinian refugees living in Lebanon do not appear to influence growth of infants younger than two years of age but may contribute to the growth deficit in older children.

Interchangeability of pencil-beam and fan-beam dual-energy X-ray absorptiometry measurements in piglets and infants.

BACKGROUND: Compared with the older pencil-beam (PB) dual-energy X-ray absorptiometry (DXA), the newer fan-beam (FB) DXA has the advantage of faster scan acquisition and greater accuracy of body-composition measurement in small subjects. However, no data exist on the relation between the measurements obtained with these techniques. OBJECTIVE: The objective of the study was to investigate whether PB and FB DXA measurements in small subjects are interchangeable. DESIGN: PB and FB DXA scans were performed on 26 piglets and 54 infants to examine the relation between the measurements obtained by using the 2 techniques. RESULTS: The correlation between all PB and FB DXA measurements of variables (total weight, bone area, bone mineral content, bone mineral density, and lean and fat masses) approached 1.0, but there were significant differences in absolute values. The extent of the differences varied according to the variable, with the lowest value for total weight (mean difference: approximately 1% for both piglets and infants) and the highest value for bone mineral content (mean difference: 35.3% and 36.7% for piglets and infants, respectively). PB and FB DXA measurements were strongly predictive of each other after adjustment (r(2) = 0.927-1.000 for the piglet data and 0.939-0.999 for the infant data). CONCLUSION: In small subjects, DXA measurements from PB and FB techniques were strongly predictive of each other, although their absolute values differed. Thus, group comparison of PB and FB DXA data is possible after adjustment of the data from either technique. It is advisable to generate normative data for each technique and to use the same technique throughout longitudinal studies.

Technical considerations for fan-beam dual-energy x-ray absorptiometry body composition measurements in pediatric studies.

BACKGROUND: A piglet model was used to determine the influence of frequently encountered situations in clinical studies of infants and young children on fan-beam dual-energy x-ray absorptiometry (DXA) measurements. METHODS: DXA scans of piglets (640 g to 21,100 g) were acquired in the infant and adult mode and were analyzed with 1 infant, 1 pediatric, and 3 versions of adult software. RESULTS: The effect of repositioning of the piglets from the center to the periphery of the scanning table on DXA measurements included an average difference of up to 0.5% for total weight, 5.0% for bone mineral content, 5.6% for bone mineral density, 1.3% for lean mass, and 21.9% for fat mass (< or = .05, all comparisons) although no significant changes occurred when the piglets were scanned in symmetrical positions on either edge of the scanning table. Different posture (prone vs supine and side), varied number of blankets overlaid or wrapped around the piglet, and parenteral but not enteral bolus feeding could significantly alter fan-beam DXA measurements to varying extents. Adult and pediatric software underestimated bone area and bone mineral content but overestimated bone mineral density, lean mass, fat mass, and total weight compared with infant software measurements. However, strong predictive relationships among these fan-beam DXA data in subjects >10 kg allow systematic corrections of data from different scan modes and different software. CONCLUSIONS: Attention to details and consistency in the technique for scan acquisition and analysis are critical to the generation of meaningful data and to allow for detection of true differences in DXA measurements of small subjects.

Body composition of neonates from fan beam dual energy X-ray absorptiometry measurement.

BACKGROUND: Fan beam dual energy x-ray absorptiometry (FB DXA) has recently been validated for the measurement of body composition in small subjects. This study represents the first report of body composition (bone mineral content, fat mass, and lean mass) in human neonates measured by FB DXA. METHODS: FB DXA measurements were performed in 73 healthy singleton neonates with mean +/- SD birth weights 3354 +/- 316 g (range, 2720 to 3982 g) and gestational ages 39.5 +/- 1.2 weeks (range, 37 to 42 weeks). There were 26 white (11 male infants, 15 female infants), 42 African American (17 male infants, 25 female infants), and 5 Hispanic (4 male infants, 1 female infant) infants. The predictive ability of physiologic parameters to predict body composition measurements was determined with regression analysis. RESULTS: The mean +/- SD for bone mineral content was 89.3 +/- 14.1 g, fat mass was 485 +/- 14.1 g, and lean mass was 2898 +/- 281.5 g. Weight was significantly correlated with all DXA measurements and was the single best predictor of body composition. Weight alone contributed 32% to 98% of the variance of the DXA measured parameters. Gender, race, and length were additional predictors that could be forced into a predictive equation for selected DXA dependent variables according to statistical significance. An independent gender effect was also demonstrated, with male infants having higher lean mass but lower fat mass. CONCLUSIONS: Our data in human neonates demonstrated the ability of FB DXA to measure body composition. Body weight is the best physiologic predictor of overall body composition. There is also an independent gender effect on soft tissue body composition.

Lumbar spine bone measurements in infants: whole-body vs lumbar spine dual X-ray absorptiometry scans.

Availability of software delineation of the lumbar spine region from infant whole-body (IWB) dual energy X-ray absorptiometry scan offers an opportunity to gain additional information at the lumbar spine without a separate scan, although the validity of this technique has never been tested. Lumbar spine measurements derived from IWB scans using software-delineated first to fourth lumbar vertebrae, and from specific infant spine (IS) scans, were determined in 111 infants using two pencil-beam densitometers. Intraoperator repeatability determined by reanalysis of 10 pairs of IWB and IS scans from each densitometer. Lumbar spine area, bone mineral content, and bone mineral density from IWB and IS scans were significantly correlated r = 0.68-0.95, p < 0.001 for all comparisons) but show poor agreement (Bland-Altman method) with one SD of the differences equal to 26-55% of the mean. Intraoperator reanalysis shows good agreement with one SD of the differences from IWB scans at <7% of the mean, and <2.9% from IS scans. Findings were the same for both densitometers. We conclude that lumbar spine bone measurements from IWB or IS scans are highly reproducible and significantly correlated but data from IWB scans cannot substitute for data from IS scans.

Quantitative bone US measurements in neonates and their mothers.

BACKGROUND: Factors that affect quantitative ultrasound (QUS) bone measurements have not been clearly defined for all clinical populations. OBJECTIVE: To determine some technical and clinical aspects that may affect QUS bone measurement in the neonate-maternal dyad. MATERIALS AND METHODS: Speed of sound (SOS) was measured at the radius and tibia using a commercial multisite axial transmission QUS instrument and three manufacturer-provided probes (CS, CR and CM). RESULTS: The study included 183 singleton neonates and 159 mothers. The type of probe, weight and edema significantly affected SOS measurements. In infants, the CS and CR probes measured SOS consistently at the tibia but not the radius. Gestational age was predictive of SOS from the CS probe and remained significant when race, gender, and birth weight were included. None of these parameters predicted SOS when using the CR probe. Maternal SOS at the radius and tibia was correlated with the CM probe. Maternal SOS was predicted by age but not by gravid status, number of living children, or race. There was no consistent correlation between maternal-infant dyad SOS measurements. CONCLUSIONS: Axial transmission SOS of bone varies with probe and site and is affected by technical and clinical factors. Valid data depend on documentation of the probes used and the clinical population studied.

Palm olein in the fat blend of infant formulas: effect on the intestinal absorption of calcium and fat, and bone mineralization.

OBJECTIVE: To evaluate the published clinical data on the physiologic effects of using palm oil and its low melting fraction, palm olein (PO) as a dominant lipid source in the fat blend in infant formulas. DESIGN: A systematic search of Medline and the Cochrane Database of Systematic Reviews was performed to retrieve studies comparing infants who received infant formulas containing PO with those who received infant formulas without PO or which contained synthetic triacylglyceride as a source of palmitic acid. Outcomes of interest include intestinal fractional absorption of fat, palmitic acid and calcium; and bone mass. The effect size for each dependent variable in each published study was obtained by standardizing based on the difference in means between non-PO and PO group with respect to the standard deviation of the PO group. Trend analysis of the outcome of interest was performed when 3 or more between group comparisons were available. The comparison of effect size across different studies was based on all available data and includes results that showed no significant difference between infants fed PO or non-PO study formulas in the outcomes of interest. RESULTS: Nine publications were identified with non-PO and PO comparison groups. The gestational ages of infants in the published studies were between 28 to 42 weeks and postnatal ages were birth to 192 days at study onset. Within each published study, there was some variability in the effect size between non-PO and PO groups. The standardized results were consistently significantly (p < 0.05) positive in favor of the feeding with non-PO formulas with respect to increased intestinal fractional absorption of fat, palmitic acid and calcium. The latter two variables were significantly different by at least 0.6 SD. Bone mass measured as total body bone mineral content was significantly higher in the non-PO group by at least 0.3 SD. CONCLUSION: The use of PO in infant formulas to match the human milk content of palmitic acid has unintended physiological consequences including diminished intestinal absorption of fat, palmitic acid and calcium and lower bone mass. The avoidance of PO or its substitution with synthetic triacylglyceride in infant formulas can prevent this detrimental effect.

Bone, lean and fat mass of newborn twins versus singletons.

AIM: Twin gestations are associated with disturbed fetal growth. The aim of this study was to compare body composition measurements of twins to those of singletons. METHODS: Anthropometric and dual energy X-ray absorptiometry (DXA) measurements were performed in twins and in matched singleton neonates. There were 48 pairs of twins in which 76 infants were appropriate for gestational age (AGA) with birth weights between the 10th and 90th percentile and 20 were small for gestational age (SGA) with birth weights <10th percentiles. Each AGA twin was matched as closely as possible for birth weight to an AGA singleton. Each SGA twin was matched with two cohorts of AGA singletons: one with similar birth weight and one with similar gestation. RESULTS: For AGA twins and their singleton cohort matched for birth weights, profile analysis using repeated measure analysis of variance showed that there were no significant differences in bone, fat and lean mass either as absolute values or as percentage of total weight. This was also the case for body composition of SGA twins compared to singletons matched for birth weight. In contrast, SGA twins have significantly lower absolute amounts of lean with tendency to lower fat and bone mass. CONCLUSION: For clinically normally grown neonates, with comparable weight, the body composition with respect to bone, fat and lean mass components are similar regardless whether they are products of singleton or twin pregnancies.

Growth, tolerance and biochemical measures in healthy infants fed a partially hydrolyzed rice protein-based formula: a randomized, blinded, prospective trial.

OBJECTIVE: To evaluate growth, tolerance and plasma biochemistries in infants fed an experimental rice protein-based infant formula. DESIGN: Randomized, blinded, 16 week parallel feeding trial of 65 healthy infants fed either an experimental partially hydrolyzed rice protein-based infant formula fortified with lysine and threonine (RPF, n = 32), or a standard intact cow's milk protein-based formula (CMF, n = 33) as a control. Assessments occurred at enrollment (average 2 days), 2, 4, 8, and 16 weeks of age. RESULTS: Growth as indicated by weight, length, and head circumference was not different between the 2 formula groups. All plasma biochemistries for both groups were within reference normal range. However, RPF group had lower phosphorus and urea nitrogen, lower essential amino acids except threonine, which was higher, and lower ratio of essential (including semi-essential) to non-essential amino acids. Differences in the concentrations and ratios of amino acids became less as feeding progressed with age. Plasma total protein, albumin, prealbumin, calcium, magnesium, and alkaline phosphatase were not different between groups. CONCLUSION: Healthy infants fed an experimental partially hydrolyzed rice protein-based formula had normal growth, tolerance, and plasma biochemistry comparable to those of infants fed a standard intact milk protein-based formula, despite some differences in amino acid profiles.

Efficacy and safety of docosahexaenoic acid and arachidonic acid addition to infant formulas: can one buy better vision and intelligence?

Long chain polyunsaturated fatty acids (LCPUFA) namely arachidonic acid (ARA, 20:4n-6) and docosahexaenoic acid (DHA, 22:6n-3) are highly concentrated in the phospholipid bilayer of biologically active brain and retinal neural membranes and are important in phototransduction and neuronal function. The rationale for adding these LCPUFA to infant formula (IF) was primarily because of their presence in large quantities in the retina and brain and in human milk. In addition, infants fed IF containing LCPUFA and breastfed infants have comparable ARA and DHA levels in red cell and plasma, in contrast to the lower ARA and DHA levels in those fed IF containing only the essential fatty acids: linoleic (LA, 18:2n-6) and linolenic (LNA, 18:3n-3), the precursors to ARA and DHA, respectively. However, functional benefits in particular visual or neural development from IF containing LCPUFA remains controversial. Potential for excessive and/or imbalanced intake of n-6 and n-3 fatty acids exists with increasing fortification of LCPUFA to infant foods other than IF.

Use of fan beam dual energy x-ray absorptiometry to measure body composition of piglets.

A piglet model was used to determine whether the fan beam dual energy X-ray absorptiometry technique (DXA) could be adapted for the measurement of body composition of small subjects. Commercial domestic swine piglets (n = 14) with weights between 1.95 and 21.1 kg had duplicate fan beam-DXA scans followed by chemical analysis of body composition. Each scan required 2-3 min to complete. DXA-measured total body weight was validated against scale weights of the piglets (with and without blanket and other covering), DXA bone mineral content validated against carcass ash and calcium, and DXA lean and fat mass validated against chemical lean and fat contents. Measurements from duplicate DXA scans were highly reproducible with adjusted r(2) values from 0.992 to 1.000. Each DXA measurement was highly predictive of the scale weight or specific chemical body composition with adjusted r(2) values from 0.974 to 0.999. The intraclass reliability coefficient among measurements from individual scans with scale weight or the weight of individual chemical components was extremely high at > or =0.99 for all comparisons. The SD of residuals for DXA prediction of scale weights (with and without covering) were 168 and 157 g, respectively, and were 27, 8.8, 122 and 72 g for the prediction of carcass ash, calcium, lean and fat tissue content, respectively. We conclude that rapid scan acquisition, accurate and precise prediction of scale weight and components of body composition would support the use of fan beam-DXA for body composition studies in growing humans or animals.

Validation of bone mass and body composition measurements in small subjects with pencil beam dual energy X-ray absorptiometry.

OBJECTIVE: To validate the most widely reported dual energy X-ray absorptiometry (DXA) technique for the measurement of bone mass and body composition in human infants with a piglet model. METHODS: Duplicate scans were obtained in 13 piglets (1950g to 21100g) using a whole body densitometer (Hologic QDR 2000 plus, Hologic Inc., Waltham, MA) operated in the pencil-beam mode on a two platform (aluminum platform overlying a foam table pad) system. DXA measurements that included total weight, bone mineral content, fat and lean mass were compared with carcass weight and chemical analysis for ash and calcium content, fat and lean mass. RESULTS: Measurements from duplicate DXA scans were nearly perfectly correlated (r = 0.98 to 1.00). DXA measurements were strongly predictive of scale weight and chemical composition for all piglets (adjusted r(2) = 0.93 to 1.00, intraclass reliability coefficients = 0.943 to 0.999, p < 0.001 for all comparisons) although DXA bone mineral content consistently underestimated carcass ash and calcium content. Measured values from heavier piglets were not significantly different from values predicted from the lighter piglets' data. Slopes from regression based on lighter versus heavier piglets were not significantly different except for the bone mineral content with carcass ash or calcium content. CONCLUSION: Our study validated the use of pencil beam DXA and its ability to determine relative changes in bone mass and body composition measurements over a much greater range of body weight than previous reports although its use as a direct indicator of nutrient requirement may be limited.

Dual energy X-ray absorptiometry measurements in small subjects: conditions affecting clinical measurements.

OBJECTIVE: To document the clinical and experimental situations that may affect DXA measurements in small subjects. METHODS: 49 piglets (886g to 21100g) had measurements with either of two pencil beam densitometers (QDR 1000W and QDR 2000 Plus, Hologic Inc, Waltham, MA) using commercial infant (IWB) and adult whole body (AWB) software v5.71p and v5.71 respectively. AWB scans were analyzed with three additional software versions. 35 infants (2115 to 11564g) had IWB measurements. RESULTS: DXA measurements of total weight, bone mineral content, bone area, bone mineral density, fat and lean mass from IWB scans (all piglets) and from AWB scans (piglets >12 kg) were highly reproducible (p < 0.001). A statistically significant change occurred in at least one of the DXA measurements from the use of different platforms, variations in the amount and placement of covering (e.g., blanket), placement of the external calibration standard, presence of radiographic contrast material, presence of movement artifact, delivery of an intravenous fluid bolus prior to scanning or improper delineation of external calibration standard during analysis. Additionally, results varied amongst different versions of software as well as between IWB and AWB softwares. CONCLUSION: In small subjects, consistency in the DXA techniques is paramount for valid and meaningful comparison of DXA data in bone mass and body composition.

Body composition in neonates: relationship between measured and derived anthropometry with dual-energy X-ray absorptiometry measurements.

This study examined the relationship between measured and derived anthropometric measurements with dual-energy X-ray absorptiometry measured lean and fat mass at 3.0 +/- 2.8 (SD) days in 120 neonates with birth weights appropriate (AGA; n=74), large (LGA; n=30); or small (SGA, n=16) for gestational age. Anthropometric measurements, including total body weight and length, and regional measurements, including circumferences of head, chest, abdomen, midarm, and midthigh and dynamic skinfold thickness (15 and 60 s) at tricep, subscapular, suprailiac, and midthigh, were performed. Derived anthropometry included muscle and fat areas, and ratios were calculated from direct measurements. The skinfold thickness measurements between 15 and 60 s were highly correlated (r=0.973-0.996, p <0.001 for all comparisons). Strong correlations existed within the four circumferences of trunk and extremities, the four skinfolds, and the ratios of weight to length and its higher powers. Weight and length accounted for >97% of the variance of lean mass in AGA and SGA infants and 46% of the variance in LGA infants and for 80, 82, and 84% of the variance of fat mass in SGA, AGA, and LGA infants, respectively, whereas midarm:head circumference ratio and arm muscle and fat areas are the most important derived anthropometry in the prediction for body composition. They independently accounted for up to 16.5 and 10.2%, respectively, of the variance in body composition depending on the state of in utero growth. Thus, total body weight and length and some selected regional and derived anthropometry accounted for the vast majority of the variance of body composition.

Fan beam dual energy X-ray absorptiometry body composition measurements in piglets.

OBJECTIVES: A piglet model was used to validate and cross validate the fan-beam (FB) dual energy X-ray absorptiometry (DXA) software vKH6 and to determine the predictive values of physiologic parameters (weight, length, age and gender) on body composition. METHODS: Nineteen piglets (Group A: 600 to 21100 g) were used to validate the FB-DXA measurements of body composition based on chemical analysis of the carcass. An additional 22 piglets (Group B: 640 g to 17660 g) had FB-DXA measurements, and these values were compared to the predicted values generated from regression equations computed from group A piglets. Body composition for bone mass, lean mass and fat mass was based on ash weight, nitrogen and fat measured from three aliquots of homogenate from each carcass. Data from all piglets (n = 41) were used to determine the variations in body composition. Data analysis used regression, t test and analysis of variance. RESULTS: Duplicate DXA (total weight TW, bone mineral content BMC, bone area BA, bone mineral density BMD, lean mass LM and fat mass FM) measurements were highly correlated (r = 0.98 to 1.00, p < 0.001 for all comparisons) and were not significantly different. No significant differences were found in the residuals from predicted versus measured DXA values between the larger and the smaller (<1.6 kg) piglets from Group A. For Group B piglets, the DXA measured TW of 5666 +/- 5692 g (mean +/- SD), LM (5063 +/- 5048 g), FM (465 +/- 510 g), BMC (138 +/- 139 g), BA (486 +/- 365 cm(2)) and BMD (0.235 +/- 0.071 g/cm(2)) were highly significantly correlated with (r = 0.94 to 1.00, p < 0.001 for all comparisons) and were not significantly different from the predicted values. Data from all piglets (n = 41) showed that weight is the dominant predictor of whole body and regional body composition. Length, age or gender contributed to <2% of the variability of body composition. CONCLUSION: Body composition measurements using the FB DXA software vKH6 is highly reproducible. The software vKH6 is validated for use in a wide range of body weights and body composition, and cross-validated using a separate group of animals. Body weight is the dominant predictor of body composition in immature piglets.