Assessment of dual-energy X-ray absorptiometry measures of bone health in pediatric chronic kidney disease.
Department of Pediatrics, Children's Hospital of Philadelphia, 3535 Market Street, Room 1564, Philadelphia, PA 19104, USA. Pediatric Nephrology
(Impact Factor: 2.86).
02/2012; 27(7):1139-48. DOI: 10.1007/s00467-012-2116-x
Dual-energy X-ray absorptiometry (DXA) techniques are limited in childhood chronic kidney disease (CKD) by the confounding effect of short stature and opposing parathyroid hormone effects on trabecular and cortical bone. Peripheral quantitative computed tomography (pQCT) is not subject to these limitations.
Lumbar spine (LS) and whole-body (WB) DXA and tibia pQCT scans were obtained in 88 stage 4-5 CKD and >650 healthy participants, ages 5-21 years. Sex- and race-specific Z-scores were generated for bone mineral density (BMD) and bone mineral content (BMC) by DXA, relative to age and adjusted for height Z-score (LS-BMD-Z and WB-BMC-Z), and compared to pQCT Z-scores for trabecular BMD (TrabBMD-Z) for age and cortical BMC (CortBMC-Z) for age and tibia length.
LS-BMD-Z [0.50 (95% C.I. 0.28, 0.73), p<0.0001] and TrabBMD-Z [0.53 (0.27, 0.79), p<0.0001] were greater in CKD, and WB-BMC-Z [-0.36 (-0.53, -0.19), p<0.0001] and CortBMC-Z [-0.48 (-0.70, -0.27), p<0.0001] were lower, compared to reference participants. Z-scores were correlated at trabecular (LS-BMD-Z and TrabBMD-Z: R=0.36) and cortical (WB-BMC-Z and CortBMC-Z: R=0.64) sites in CKD; similar to correlations in reference participants.
Lumbar spine and whole-body DXA suggested greater trabecular BMD and lower cortical BMC in CKD, consistent with pQCT results; however, correlations were modest. Studies are needed to identify methods that predict fracture in childhood CKD.
Available from: Justine Shults
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ABSTRACT: The impact of pediatric chronic kidney disease (CKD) on acquisition of volumetric bone mineral density (BMD) and cortical dimensions is lacking. To address this issue, we obtained tibia quantitative computed tomography scans from 103 patients aged 5-21 years with CKD (26 on dialysis) at baseline and 12 months later. Gender, ethnicity, tibia length, and/or age-specific Z-scores were generated for trabecular and cortical BMD, cortical area, periosteal and endosteal circumference, and muscle area based on over 700 reference subjects. Muscle area, cortical area, and periosteal and endosteal Z-scores were significantly lower at baseline compared with the reference cohort. Cortical BMD, cortical area, and periosteal Z-scores all exhibited a significant further decrease over 12 months. Higher parathyroid hormone levels were associated with significantly greater increases in trabecular BMD and decreases in cortical BMD in the younger patients (significant interaction terms for trabecular BMD and cortical BMD). The estimated glomerular filtration rate was not associated with changes in BMD Z-scores independent of parathyroid hormone. Changes in muscle and cortical area were significantly and positively associated in control subjects but not in CKD patients. Thus, children and adolescents with CKD have progressive cortical bone deficits related to secondary hyperparathyroidism and potential impairment of the functional muscle-bone unit. Interventions are needed to enhance bone accrual in childhood-onset CKD.Kidney International advance online publication, 3 October 2012; doi:10.1038/ki.2012.347.
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The aim of the present study was to determine the prevalence and predisposing factors for vitamin D deficiency and low bone mineral density (BMD) in patients with intestinal failure (IF).
A retrospective review of patients with IF managed at the Cincinnati Children's Hospital Medical Center. IF was defined as history of parenteral nutrition (PN) >30 days. Vitamin D deficiency was defined as serum 25-hydroxyvitamin D (25 (OH) D) <20 ng/dL. Reduced BMD was defined using dual x-ray absorptiometry z score ≤-2. A binary logistic regression model was used to test for association of significant risk factors and the outcome variables after univariate analyses.
One hundred and twenty-three patients with median age of 4 years (range 3-22 years) were evaluated. Forty-nine (39.8%) patients had at least a documented serum 25 (OH) D deficiency during the study interval, whereas 10 of 80 patients (12.5%) with dual x-ray absorptiometry scans completed had a low BMD z score. Age at study entry was associated with both 25 (OH) D deficiency (P = 0.01) and low BMD z score (P = 0.03). Exclusive PN at study entry was associated with reduced bone mass (P = 0.03). There was no significant association between vitamin D deficiency and low BMD z score (P = 0.31).
The risk of 25 (OH) D deficiency and low BMD z score increases with age among patients with IF. Strategies for monitoring and preventing abnormal bone health in older children receiving exclusive PN need to be developed and evaluated.
Available from: Babette Zemel
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ABSTRACT: This prospective study evaluated changes in dual energy X-ray absorptiometry (DXA) whole body bone mineral content (WB-BMC) and spine areal bone mineral density (spine-BMD), and tibia quantitative computed tomography (QCT) trabecular and cortical volumetric BMD and cortical area in 56 children over 12 months following renal transplantation. At transplant, spine-BMD Z-scores were greater in younger recipients (<13 years), versus 898 reference participants (p < 0.001). In multivariate models, greater decreases in spine-BMD Z-scores were associated with greater glucocorticoid dose (p < 0.001) and declines in parathyroid hormone levels (p = 0.008). Changes in DXA spine-BMD and QCT trabecular BMD were correlated (r = 0.47, p < 0.01). At 12 months, spine-BMD Z-scores remained elevated in younger recipients, but did not differ in older recipients (≥13) and reference participants. Baseline WB-BMC Z-scores were significantly lower than reference participants (p = 0.02). Greater glucocorticoid doses were associated with declines in WB-BMC Z-scores (p < 0.001) while greater linear growth was associated with gains in WB-BMC Z-scores (p = 0.01). Changes in WB-BMC Z-scores were associated with changes in tibia cortical area Z-scores (r = 0.52, p < 0.001), but not changes in cortical BMD Z-scores. Despite resolution of muscle deficits, WB-BMC Z-scores at 12 months remained significantly reduced. These data suggest that spine and WB DXA provides insight into trabecular and cortical outcomes following pediatric renal transplantation.
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