TOTAL-BODY CALCIUM AND BONE-MINERAL CONTENT - COMPARISON OF DUAL-ENERGY X-RAY ABSORPTIOMETRY WITH NEUTRON-ACTIVATION ANALYSIS

The aim of this study was to compare the dual-energy X-ray absorptiome try (DXA) measurement of bone mass with an independent measure of body calcium obtained by neutron activation analysis (NAA), Total body bon e mineral content (BMC) was measured using DXA in 46 subjects in the a ge range 5-47 years (17 children, 28 young women, and 1 adult male), T otal body calcium (TBCa) was measured in the same subjects by in vivo NAA, The correlation between the two measures of bone mass was highly significant (BMC[g] = 3.22 x TBCa[g] - 51.4, r > 0.98, p < 0.0001, SEE (BMC) = 122.7 g), When BMC nas the independent parameter, the SEE(TBCa ) was 37.5 g, Bland-Altman analysis indicated a mean difference of 2.8 g with a standard error +/-4.7 g for TBCaNAA versus TBCaDXA when the BMC values were converted to TBCa, The relative change in bone mass (D elta TBCa/Delta BMC) for DXA was higher than that reported for dual-ph oton absorptiometry versus NAA. The findings presented in this study p rovide translational equations among the DXA and NAA measurements and for the conversion of total body BMC to TBCa in children and young adu lts.