COMPARISON OF BODY COMPOSITION MEASUREMENTS USING HOLOGIC QDR-1000 AND QDR-4500 DUAL-ENERGY X-RAY ABSORPTIOMETERS IN TEENAGERS

Abstract

PURPOSE To compare body composition measurements made using Hologic QDR-1000 pencil beam and Hologic QDR-4500 fan beam DXA in a sample of 13–18 y old white and black teenagers (n = 219). METHODS Measurements of total fat (FAT), fat-free soft tissue (FFST), bone mineral content (BMC), bone mineral density (BMD) and percent body fat (%BF) were compared between repeated measurements using the QDR-4500, and between the two scanners using mixed model ANOVA. Intraclass correlation coefficients and Bland-Altman limits of agreement were used to evaluate inter- and intra-scanner reliability. Mean measurements were compared by paired t-test, and variances were compared using Pitman's test. RESULTS Intraclass correlations (ICC) for repeated measurements using the fan beam scanner were very high, ranging from 0.997–0.999 for FAT, %BF, FFST, and BMC, and 0.987 for BMD. There were no significant differences in mean measurements between repeat scans using the QDR-4500 (p-values ranged from 0.1890 to 0.7823). Variances were significantly different between scans for BMD (p = 0.0037), but not for any other measurements (p-values 0.1769 – 0.5686). Mean measurements were significantly different between the two scanners for %BF, BMC, and BMD (p < 0.0001), but not for FAT or FFST (p = 0.7906 and 0.6590, respectively). CONCLUSION Different modes and velocities of DXA scanning may reduce precision of body composition measurement, which needs to be considered in longitudinal studies. Supported by NIH (HL64157).