Creatinine as a measure of lean body mass during treatment of acute lymphoblastic leukemia in childhood.

Protein energy malnutrition is well-recognized in children with acute leukemia and may result in loss of lean body mass (LBM) with attendant morbidities. Much of the LBM consists of skeletal muscle, the mass of which is reflected in urinary creatinine excretion. As accurate 24 hours urine collections are challenging in children, we investigated the prospect that serum creatinine concentration provides a measure of LBM. Eleven children with acute lymphoblastic leukemia were assessed at 7 time points (6-mo intervals) from diagnosis to 1 year after the completion of therapy. LBM was measured as fat-free mass by dual energy x-ray absorptiometry (DXA scans) and correlated with serum creatinine concentration and 24 hours urine creatinine excretion. As expected, there was a strong correlation between 24 hours urinary creatinine excretion and LBM from DXA scans (r=0.79, P<0.001). Serum creatinine concentration also correlated with LBM (r=0.52, P<0.001). Serum creatinine concentration provides a surrogate measure of LBM in children with acute lymphoblastic leukemia. This will be especially useful in countries with limited resources in which more sophisticated measures, such as DXA scans, are seldom available.

Whole-body bone mineral content, lean body mass, and fat mass measured by dual-energy X-ray absorptiometry in a population of normal Canadian children and adolescents.

Measurements of body composition have evident value in evaluating growing children and adolescents, and dual-energy X-ray absorptiometry (DXA) is a tool that provides accurate measurements of whole-body bone mineral content (WBBMC), lean body mass (LBM), and fat mass (FM). To interpret such measurements in the context of ill health, normative values must be available. Such information could be expected to be regionally specific because of differences in ethnic, dietary, and physical activity determinants. In this study, DXA was performed with Hologic densitometers in normal girls (n = 91) and boys (n = 88) between 3 and 18 years of age. The derivation of normal ranges is presented for boys and girls. The correlation of the sum of WBBMC, LBM, and FM with directly measured body weight was almost perfect (r > 0.997). As expected, FM and body mass index correlated strongly. The normal values for WBBMC, LBM, and FM from this study are compared with other Canadian data and with published normative data from Argentina and the Netherlands, all of which use different densitometers. The results of this study allow the calculation of z scores for each facet of body composition and facilitate the use of DXA to report routine evaluations of body composition in children and adolescents.

Age-predicted values for lumbar spine, proximal femur, and whole-body bone mineral density: results from a population of normal children aged 3 to 18 years.

We measured areal bone mineral density (BMD) with dual-energy X-ray absorptiometry (DXA) at the lumbar spine and the proximal femur and for the total body in 179 subjects (91 girls and 88 boys) with no known disorders that might affect calcium metabolism. Results are also reported for lumbar spine bone mineral content (BMC) and for the derived variable, bone mineral apparent density (BMAD). Expected-for-age values for each variable were derived for boys and girls by using an expression that represented the sum of a steady increase due to growth plus a rapid increase associated with puberty. Normal ranges were derived by assuming that at least 95% of children would be included within 1.96 population standard deviations (SD) of the expected-for-age value. The normal range for lumbar spine BMD derived from our population of children was compared with previously published normal ranges based on results obtained from different bone densitometers in diverse geographic locations. The extent of agreement between the various normal ranges indicates that the derived expressions can be used for reporting routine spine, femur, and whole-body BMD measurements in children and adolescents. The greatest difference in expected-for-age values among the various studies was that arising from intermanufacturer variability. The application of published conversion factors derived from DXA measurements in adults did not account fully for these differences, especially in younger children.

Effect of diagnostic radioisotopes and radiographic contrast media on measurements of lumbar spine bone mineral density and body composition by dual-energy x-ray absorptiometry.

Since there is almost no information on whether the concomitant use of diagnostic radioisotopes and radiographic contrast media interferes with dual-energy X-ray absorptiometry (DXA), we investigated these potentially confounding effects. At routine scheduled radiographic follow-up, 40 patients previously treated for malignant lymphomas or solid tumors in Hamilton and Ottawa, Canada were evaluated, 10 in each of the following 4 categories of diagnostic procedure: (1) computed tomography (CT) with intravenous, iodine-based contrast (+/-oral contrast), (2) magnetic resonance imaging (MRI) with gadolinium-based contrast, (3) gallium scan (GS), and (4) technetium bone scan (TBS). Whole body bone mineral content (WB-BMC) and lumbar spine bone mineral density (LS-BMD), total fat mass (TFM), and lean body mass (LBM) were measured by DXA immediately before and after the other radiological studies (on the same day) and then 7 days later. No statistically significant differences were found among WB-BMC, LS-BMD, TFM, and LBM Z-scores immediately before and after MRI, GS, TBS, and 7 days later. The DXA measurements performed immediately before and after CT showed statistically significant differences in WB-BMC (100% vs 124.5%, p<0.001), TFM (100% vs 75.4%, p<0.001), and LBM (100% vs 110%, p<0.001), resulting from the CT contrast agents compromising the precision of the DXA. The DXA results after 7 days were not statistically different from those at baseline. Dual-energy X-ray absorptiometry can be performed in association with other radiological techniques, with the exception of CT conducted with contrast within 1 week. This study provides information that applies not only to patients with cancer but to the general population undergoing diagnostic procedures.