Printer Friendly Version
Printer Friendly Version
Printer Friendly Version
A.6.01.40
Using low-dose x-rays of two different energy levels, whole-body dual-energy x-ray absorptiometry (DXA) measures lean tissue mass, total and regional body fat, as well as bone density. DXA scans have become a tool for research on body composition (eg, as a more convenient replacement for underwater weighing). This policy addresses potential applications in clinical care rather than research use of the technology.
Body Composition Measurement
Body composition measurements can be used to quantify and assess the relative proportions of specific body compartments such as fat and lean mass (eg, bones, tissues, organs, muscles). These measurements may be more useful in informing diagnosis, prognosis, or therapy than standard assessments (eg, body weight, body mass index) that do not identify the contributions of individual body compartments or their particular relationships with health and disease. While these body composition measurements have been most frequently utilized for research purposes, they may be useful in clinical settings to:
Evaluate the health status of undernourished patients, those impacted by certain disease states (eg, anorexia nervosa, cachexia), or those undergoing certain treatments (eg, antiretroviral therapy, bariatric surgery).
Evaluate the risk of heart disease or diabetes by measuring visceral fat vs total body fat.
Assess body composition changes related to growth and development (eg, infancy, childhood), aging (eg, sarcopenia), and certain disease states (eg, HIV, diabetes).
Evaluate patients in situations where body mass index is suspected to be discordant with total fat mass (eg, body-building, edema).
A variety of techniques have been researched, including most commonly, anthropomorphic measures, bioelectrical impedance, and dual-energy x-ray absorptiometry (DXA). All of these techniques are based in part on assumptions about the distribution of different body compartments and their density, and all rely on formulas to convert the measured parameter into an estimate of body composition. Therefore, all techniques will introduce variation based on how the underlying assumptions and formulas apply to different populations of subjects (i.e., different age groups, ethnicities, or underlying conditions). Techniques using anthropomorphics, bioelectrical impedance, underwater weighing, and DXA are briefly reviewed below.
Anthropomorphic Techniques
Anthropomorphic techniques for the estimation of body composition include measurements of skinfold thickness at various sites, bone dimensions, and limb circumference. These measurements are used in various equations to predict body density and body fat. Due to its ease of use, measurement of skinfold thickness is one of the most common techniques. The technique is based on the assumption that the subcutaneous adipose layer reflects total body fat, but this association may vary with age and sex. Skinfold thickness measurement precision and utility can also be affected by operator experience and a lack of applicable reference data for specific patient populations or percentile extremes.
Bioelectrical Impedance
Bioelectrical impedance analysis is based on the relation between the volume of the conductor (i.e., human body), the conductor's length (i.e., height), the components of the conductor (i.e., fat and fat-free mass), and its impedance. The technique involves attaching surface electrodes to various locations on the arm and foot. Alternatively, the patient can stand on pad electrodes. Estimates of body composition are based on the assumption that the overall conductivity of the human body is closely related to lean tissue. The impedance value is then combined with anthropomorphic data and certain other patient-specific parameters (eg, age, gender, ethnicity) to give body compartment measures. These measures are calculated based on device manufacturer-specific regression models, which are generally proprietary. Bioelectrical impedance measures can be affected by fat distribution patterns, hydration status, ovulation, and temperature.
Underwater Weighing
Underwater weighing requires the use of a specially constructed tank in which the subject is seated on a suspended chair. The subject is then submerged in the water while exhaling; the difference between weight in air and weight in water is used to estimate total body fat percentage. While valued as a research tool, weighing people underwater is typically not suitable for routine clinical use. This technique is based on the assumption that the body can be divided into 2 compartments with constant densities: adipose tissue, with a density of 0.9 g/cm³, and lean body mass (ie, muscle and bone), with a density of 1.1 g/cm³. One limitation of the underlying assumption is the variability in density between muscle and bone; for example, bone has a higher density than muscle, and bone mineral density varies with age and other conditions. Also, the density of body fat may vary, depending on the relative components of its constituents (e.g., glycerides, sterols, and glycolipids).
Dual-energy X-Ray Absorptiometry
While the cited techniques assume 2 body compartments, DXA can estimate 3 body compartments consisting of fat mass, lean body mass, and bone mass. DXA systems use a source that generates x-rays at 2 energies. The differential attenuation of the 2 energies is used to estimate the bone mineral content and the soft tissue composition. When 2 x-ray energies are used, only 2 tissue compartments can be measured; therefore, soft tissue measurements (i.e., fat and lean body mass) can only be measured in areas in which no bone is present. DXA can also determine body composition in defined regions (ie, in the arms, legs, and trunk). DXA measurements are based in part on the assumption that the hydration of fat-free mass remains constant at 73%. Hydration, however, can vary from 67% to 85%, and can vary by disease state. Other assumptions used to derive body composition estimates are considered proprietary by DXA manufacturers. Vertebral fracture assessment with densitometry by DXA is addressed separately in the Vertebral Fracture Assessment with Densitometry or Biomechanical Computed Tomography medical policy.
Body composition software for several bone densitometer systems has been approved by the U.S. Food and Drug Administration through the premarket approval process. They include the Lunar iDXA systems (GE Healthcare), Hologic DXA systems (Hologic), Mindways Software, Inc. systems (Mindways Software, Inc.), and Norland DXA systems (Swissray).
Dual-energy x-ray absorptiometry body composition studies are considered investigational.
Federal Employee Program (FEP) may dictate that all devices approved by the U.S. Food and Drug Administration (FDA) may not be considered investigational and thus these devices may be assessed only on the basis of their medical necessity.
The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.
Investigative is defined as the use of any treatment procedure, facility, equipment, drug, device, or supply not yet recognized as a generally accepted standard of good medical practice for the treatment of the condition being treated and; therefore, is not considered medically necessary. For the definition of Investigative, “generally accepted standards of medical practice” means standards that are based on credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community, and physician specialty society recommendations, and the views of medical practitioners practicing in relevant clinical areas and any other relevant factors. In order for equipment, devices, drugs or supplies [i.e, technologies], to be considered not investigative, the technology must have final approval from the appropriate governmental bodies, and scientific evidence must permit conclusions concerning the effect of the technology on health outcomes, and the technology must improve the net health outcome, and the technology must be as beneficial as any established alternative and the improvement must be attainable outside the testing/investigational setting.
6/16/2008: Policy added.
7/17/2008: Reviewed and approved by the Medical Policy Advisory Committee (MPAC).
12/31/2008: Code reference section updated per 2009 CPT/HCPCS revisions.
6/23/2010: Policy statement unchanged. FEP verbiage added to Policy Exceptions section. CPT Code 0028T was removed because the code was deleted 12/31/2008. CPT Code 76499 was added to the Non-Covered Codes Table.
04/20/2011: Policy reviewed; no changes.
01/18/2012: Policy reviewed; no changes.
04/01/2013: Policy reviewed; no changes.
03/07/2014: Policy reviewed; no changes.
01/30/2015: Policy reviewed; no changes.
07/23/2015: Code Reference section updated for ICD-10.
01/18/2016: Policy title updated to remove "DEXA." Policy description updated regarding body-composition software. Policy statement updated to change "DEXA" to "DXA." Investigative definition updated in policy guidelines section.
05/31/2016: Policy number A.6.01.40 added.
10/17/2017: Policy description updated. Policy statement unchanged.
10/04/2018: Policy reviewed; no changes.
10/22/2019: Policy description updated regarding body composition measurements. Policy description and policy statement updated to change "dual x-ray" to "dual-energy x-ray."
10/14/2020: Policy reviewed; no changes.
12/30/2021: Policy description updated regarding FDA approvals of body composition software. Policy statement unchanged.
11/30/2022: Policy description updated regarding related policies. Policy statement unchanged.
10/12/2023: Policy description updated regarding anthropomorphic techniques, bioelectrical impedance, and underwater weighing. Policy statement unchanged.
11/11/2024: Policy reviewed; no changes.
01/28/2026: Updated medical policy link in Policy Description. Policy statement unchanged.
Blue Cross & Blue Shield Association Policy # 6.01.40
This may not be a comprehensive list of procedure codes applicable to this policy.
Code Number | Description |
|---|---|
CPT-4 | |
76499 | Unlisted diagnostic radiographic procedure |
HCPCS | |
ICD-10 Procedure | |
ICD-10 Diagnosis |
CPT copyright American Medical Association. All rights reserved. CPT is a registered trademark of the American Medical Association.