Evaluation of total-body-less-head dual energy X-ray absorptiometry for the assessment of lean, fat and bone mass in athletes

Abstract

Abstract
Introduction: The routine assessment of body composition is common practice in athletic populations, particularly at the elite level. DXA is a criterion method of body composition assessment, providing precise measurements of bone mineral content (BMC), lean mass (LM) and fat mass (FM) from the standard total-body scan. More recently, a new scan application has been introduced, which measures body composition excluding the head region. The aim of this study was to investigate the precision of the new total-body less head (TBLH) application for the measurement of total body composition in athletes and compare precision with that of the standard total-body scan. The second aim was to compare the differences in total body composition outcomes between standard DXA total-body scans and TBLH scans.

Methods: This study compared in-vivo precision and total body composition outcomes from the standard total-body scan and the new TBLH scan (Lunar iDXA, GE Healthcare, Madison, WI). A total of 95 athletes (mixed sports) received repeated TBLH scans and 58 of these athletes also received standard total-body scans (overall mean age: 26.3 ± 8.8 years; male n = 63, female n=41). Participants ranged in body mass (42.7 to 129.1 kg), stature (1.55 to 2.04 m) and BMI (16.4 to 46.9 kg/m2). Precision was derived from repeat scans with re-positioning, and precision error was reported as the root mean square standard deviation (RMS±SD) and percentage co-efficient of variation (%CV).

Results: Precision error ranged from 0.38 % to 1.15 % (%CV) for standard total-body and 0.39 % to 1.28 % (%CV) for the TBLH application, depending on the body composition compartment. Body composition outcomes for the TBLH were significant lower than for the standard total body for BMC (2,865 g v 2,308 g), LM (50,276 g v 46,954 g) and FM (15,888 g v 15,183 g) , all p<0.05. Regional composition precision error was consistently lower for the TBLH application, particularly at the trunk region (TBLH = 0.54 - 2.86 %CV vs. standard total body = 0.78 - 2.57 %CV).

Conclusion: In-vivo total body composition precision of the TBLH iDXA scan is comparable to that of the standard total-body scan, and superior for regional composition assessment, in a mixed cohort of athletes. The TBLH scan may be particularly useful for monitoring body composition in athletes due to the exclusion of the head. However, new baseline measurements should be performed if centres are to adopt the TBLH method, in order to ensure consistency and validity of longitudinal measurements for the monitoring of athlete body composition. Previous body composition assessments implementing the standard total-body application should not be compared with assessments using the TBLH application.