Dual-energy X-ray absorptiometry and body composition

PURPOSE OF REVIEW: Dual-energy X-ray absorptiometry is now widely adopted for the measurement of the fat, fat-free soft tissue and bone mineral compartments of the body. Whereas it is regarded by many as a reference technique for such measurements, it is not without limitations. Inter and intra-manufacturer differences have been areas of concern. This review focuses on recent literature addressing these areas and the issue of validity. RECENT FINDINGS: Body composition measurements using newer generation dual-energy X-ray absorptiometry machines compared between different manufacturers and compared with earlier instruments continue to show differences that may be unacceptable, particularly for investigators upgrading their machines or involved in multicentre studies using different machines. In terms of validity, significant deviations at a group level are reported when compared with reference four-component models, and perhaps more importantly, wide limits of agreement are seen that are a concern for the interpretation of results at an individual level. SUMMARY: It is important that investigators recognize the limitations of dual-energy X-ray absorptiometry technology in the interpretation of their results. There is a continuing need both for inter-machine comparisons and validation studies against accepted criterion methods, particularly as new software or technological changes are introduced. Such studies permit the development of translation equations for the cross-calibration of devices, and may be vital for cross-sectional studies. For longitudinal studies in many populations, dual-energy X-ray absorptiometry is without question a valuable technique for the measurement of compositional changes, both at the total body and regional levels.