BONE-MINERAL AND BODY-FAT MEASUREMENTS BY 2 ABSORPTIOMETRY SYSTEMS - COMPARISONS WITH NEUTRON-ACTIVATION ANALYSIS

In 185 adults (68 white and 31 black males, 66 white and 20 black fema les), total body bone mineral density and content and body fat% were m easured by two dual energy X-ray absorptiometry (DXA) systems-Norland XR-26, software version 2.4, and Lunar DPX, software versions 3.4 and 3.6. In a subgroup of 18 males (10 white, 8 black), body fat% and tota l body calcium were also measured by in vivo neutron activation analys is (IVNA). For total body calcium, the DPX 3.4 system gave the highest (1239 g), IVNA the lowest (1195 g), and the XR-26 (1226 g) was not si gnificantly different from the DPX 3.6 results. For fat%, the XR-26 sy stem gave the highest estimate (23.5%), whereas measurements by the DP X 3.4 and 3.6 systems (17.4 and 18.2%) were similar to the IVNA measur ements (18.3%). BMD and BMC measurements by the two DXA systems were h ighly correlated but significantly different for the entire studied po pulation except in the case of BMC in black males.