The Official Positions of the International Society for Clinical Densitometry: Indications of Use and Reporting of DXA for Body Composition

Abstract

The technique of body composition by dual-energy X-ray absorptiometry (DXA) has been used for several years in the research environment. Its ability to accurately and precisely measure lean, fat, and mineral composition in various body compartments has been well validated. Furthermore, the technique is widely available to clinical patients on existing DXA instruments throughout the world through the use of specific software packages and scanning algorithms. There have been few clear statements regarding the clinical indications for body composition measurement in patients outside the research setting. This is in part because of the lack of specific documented interventions that would be affected by body composition test results, beyond usual clinical advice. We have examined a few of the most common, specific scenarios (HIV therapy, sarcopenia, bariatric surgery, obesity) and proposed indications for body composition assessment. We have also discussed contraindications to body composition testing.

Introduction

The task force addressed questions related to the clinical indications for body composition testing that could be supported by the published literature. Specific areas of focus were indications for body composition testing in persons living with HIV, patients after bariatric surgery, obese patients, anorexia, and sarcopenia. In addition, we searched the literature on other techniques for estimating body composition and contraindications to dual-energy X-ray absorptiometry (DXA) body composition testing. The references obtained were augmented by other pertinent references known by committee members but not appearing in the search strategy. Appendix lists the search terms used and the citations obtained. Relevant publications were downloaded and reviewed; the results collated in a data table. Presentations to the expert panel were formulated from this. The final positions agreed on by the expert panel were then brought into the document with the references supporting the final official positions.

Using DXA technology for body composition analysis has the potential to offer new diagnostic insights for patient disease in a variety of areas. In addition, the technology has the potential to monitor change with therapy or other interventions. Other technologies that measure body composition include computed tomography (CT), magnetic resonance imaging (MRI), bioelectrical impedance analysis (BIA), air/water displacement, and anthropometric measurements. Each of these techniques has unique strengths and limitations, with trade-offs in ease of use, accessibility, accuracy, and comprehensiveness. DXA is well correlated with CT, MRI, and BIA 1, 2, 3, 4, 5, 6 and should be considered when quantitative body composition measurement is desired 7, 8, 9. In some instances, use of body composition technologies other than DXA may be superior 2, 10. For example, CT and MRI offer more detailed measurements of specific regions or tissues, such as visceral adipose fat or fat infiltration of tissues 8, 9. Although most DXA software will allow for an estimate of visceral adipose tissue, the level of detail is inferior to that of CT or MRI 11, 12. Nevertheless, DXA may be preferred as the whole body may be easily quantified, radiation exposure is low, and it is likely to be more accessible and more economical to obtain than CT or MRI 1, 7, 8. As noted earlier, BIA is also widely available for body composition assessment; its advantage over DXA is portability, device cost, and ease of administration (8). Although less portable, air and water displacement systems generate similar measurements using a different technique (13). However, the inability of these methods to independently obtain measurement of more than fat or fat-free mass limits their utility. More recent versions of BIA technology have improved ability to assess regions and differentiate inter- and intracellular water 14, 15. In general, anthropometric methods are useful to assess cardiovascular disease and diabetes risk (16) and are considered crude tools to assess body composition. The strengths and limitations of these technologies are summarized in Table 1.

As DXA is demonstrated to be a viable method to measure body composition, it was deemed appropriate to address the lack of consistent guidelines recommending indications for DXA body composition and for standardized reporting of these measurements. In this endeavor, the lack of well-designed comparative studies of the modalities described earlier is acknowledged as noted in the evidence and strength of recommendation grades associated with these positions. Although there are good data validating and correlating the tools, there are no head-to-head studies evaluating comparability in a specific circumstance. Consequently, in many cases, the guidelines presented in this work will be based on clinical research studies from small numbers of patients and often lack endpoint validation or cost-efficacy data.

The task force was charged with developing recommendations for several conditions and diseases where body composition analysis by DXA may prove valuable. These conditions include people living with HIV, obesity, postbariatric surgery or weight loss, and sarcopenia. Performance athletes may benefit from applications of body composition analysis by DXA as an aid to training, but this has been addressed by others (17) and, consequently, was not addressed by this group.