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MP 6.01.40 Whole Body Dual X-Ray Absorptiometry (DEXA) to Determine Body Composition

Medical Policy

 

 

Section
Radiology

Original Policy Date
07/17/03

Last Review Status/Date
reviewed with literature
search/12:2014

Issue
12:2014

  Return to Medical Policy Index

Disclaimer

Our medical policies are designed for informational purposes only and are not an authorization, or an explanation of benefits, or a contract.  Receipt of benefits is subject to satisfaction of all terms and conditions of the coverage.  Medical technology is constantly changing, and we reserve the right to review and update our policies periodically.


Description

 

Measurements of body composition have been used to study how lean body mass and body fat change during health and disease and have provided a research tool to study the metabolic effects of aging, obesity, and various wasting conditions such as occurs with acquired immune deficiency syndrome or postbariatric surgery. A variety of techniques has been researched, including most commonly, anthropomorphic measures, bioelectrical impedance, and dual x-ray absorptiometry (DEXA) scans. All of these techniques are based in part on assumptions regarding 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, ie, different age groups, ethnicities, or underlying conditions. Anthropomorphic, bioimpedance, and DEXA techniques are briefly reviewed as followed.

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 commonly used 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.

Bioelectrical Impedance

Bioelectrical impedance is based on the relationship between the volume of the conductor (ie, the human body), the conductor's length (ie, height), the components of the conductor (ie, fat and fat-free mass), and its impedance. 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 to give body compartment measures. The technique involves attaching surface electrodes to various locations on the arm and foot. Alternatively, the patient can stand on pad electrodes.

Underwater Weighing

Underwater weighing (UWW) has generally been considered the reference standard for body composition studies. This technique 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. While valued as a research tool, UWW is obviously not suitable for routine clinical use. UWW is based on the assumption that the body can be divided into 2 compartments with constant densities, ie, adipose tissue with a density of 0.9g/cm 3 and lean body mass (ie, muscle and bone) with a density of 1.1g/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. In addition, the density of body fat may vary, depending on the relative components of its constituents, eg, glycerides, sterols, and glycolipids.

Dual X-Ray Absortiometry

While the cited techniques assume 2 body compartments, DEXA can estimate 3 body compartments consisting of fat mass, lean body mass, and bone mass. DEXA 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 (ie,, fat and lean body mass) can only be measured in areas in which no bone is present. DEXA also has the ability to determine body composition in defined regions, ie, in the arms, legs, and trunk. DEXA 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 be variable in certain disease states. Other assumptions used to derive body composition estimates are considered proprietary by DEXA manufacturers (ie, Lunar, Hologic, and Norland).

Regulatory Status

Various devices are commercially available. For example, in October 2003, the Hologic QDR®-3000 Explorer™ X-Ray Bone Densitometer (Hologic, Bedford, MA) was cleared for marketing by the U.S. Food and Drug Administration (FDA) through the 510(k) process. FDA determined that this device was substantially equivalent to existing devices for use in measurement of bone mineral content, estimation of BMD, comparison of measurements with reference databases, estimation of fracture risk, body composition analysis, and measurement of periprosthetic BMD.

 


Policy

Dual x-ray absorptiometry (DEXA) body composition studies are considered investigational.


Policy Guidelines

Prior to 2009, there was a category III CPT code 0028T specifically identifies DEXA body composition studies. This code was deleted effective 12/31/08. This service should now be coded using the unlisted CPT code 76499.


Benefit Application
BlueCard/National Account Issues

State or federal mandates (e.g., 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.


Rationale

This policy was originally created in 2003 and was updated regularly with searches of the MEDLINE database. Most recently, the literature was reviewed through October 15, 2014. The key literature is described next.

Several different clinical roles for whole body dual x-ray absorptiometry (DEXA) scans to assess body composition have been suggested. Each clinical application requires different data for analysis.

DEXA as Reference Standard for Body Composition Assessment

In general, reference standards for diagnostic tests, often used primarily in research settings, serve to evaluate and verify the use of simpler and more convenient alternative tests that measure the same diagnostic parameter. For body composition studies, underwater weighing has been historically considered the reference standard. The emergence of DXA as a potential new reference standard reflects its ease of use and the fact that it provides a 3-compartment model of body density, ie, lean body mass, bone mass, and fat mass, compared with the 2-compartment model of underwater weighing. More recently, a 4-compartment model has been suggested as the reference standard, consisting of measurements of bone/mineral, protein, water, and fat. Studies to evaluate different techniques of measuring the same parameter typically consist of correlation studies that compare values between the 2 techniques. However, correlation studies do not provide information on which diagnostic technique more closely represents the true value. For example, a lack of correlation between DXA and underwater weighing may reflect the lack of accuracy of the latter technique, as opposed to any deficiency in the DXA technique. Furthermore, 2 diagnostic techniques may be highly correlated but produce different values of body composition ie, they might identify different groups of patients with abnormal values.

There is extensive literature comparing DXA with other techniques for assessing body composition, most commonly underwater weighing, bioelectrical impedance, or skinfold thickness in different populations of patients, ie, different age groups, ethnicities, and underlying disorders.(1-8) In some cases, studies compare other techniques with DXA to identify simpler methods of determining body composition. In general, these studies have shown that DXA is highly correlated to various methods of body composition assessment. For example, one study published in 2014 compared 2 bioelectrical impedance devices with DXA for the evaluation of body composition in heart failure.(1) Another 2014 study compared bioelectric impedance analysis with DXA for evaluating body composition in adults with cystic fibrosis.(2)

Regardless of whether a DXA scan is considered the reference standard, the key consideration regarding its routine clinical use is whether the results of the scan can be used in the management of the patient to improve health outcomes.

DXA as a Diagnostic Test to Detect Abnormal Body Composition

As a single diagnostic measure, it is important to establish diagnostic cutoff points for normal and abnormal values. This is problematic, because normal values will require the development of normative databases for the different components of body composition (ie, bone, fat, lean mass) for different populations of patients at different ages. In terms of measuring bone mineral density (BMD), normative databases have largely focused on postmenopausal white women, and these values cannot necessarily be extrapolated to either men or to different races. DXA determinations of BMD are primarily used for fracture risk assessment in postmenopausal women and to select candidates for various pharmacologic therapies to reduce fracture risk. In addition to the uncertainties of establishing normal values for other components of body composition, it also is unclear how a single measure of body composition would be used in patient management.

DXA as a Technique to Monitor Changes in Body Composition

The ability to detect change in body composition over time is related in part to the precision of the technique, defined as the degree to which repeated measurements of the same variable give the same value. For example, DXA measurements of bone mass are thought to have a precision error of 1% to 3% and, given the slow rate of change in BMD in postmenopausal women treated for osteoporosis, it is likely that DXA scans would only be able to detect a significant change in BMD in the typical patient after 2 years of therapy. Of course, changes in body composition are anticipated to be larger and more rapid than changes in BMD in postmenopausal women; therefore, precision errors in DXA scans become less critical in interpreting results.

Several studies have used DXA to monitor changes in body composition over time in a clinical patient population; none of these used DXA findings to make patient management decisions or addressed how serial body composition assessment might improve health outcomes.(9,10) For example, in 2014, Franzoni et al published a prospective study evaluating body composition in adolescent females with restrictive anorexia nervosa.(10) Patients underwent DXA at baseline and 12 months after treatment for their eating disorder. A total of 46 of 79 patients (58%) completed the study. Mean total fat mass was 21% at baseline and 25% after 1 year, and this increase was statistically significant in all body regions. Change in fat mass percentage was significantly correlated with change in BMI.

Summary of Evidence

Dual x-ray absorptiometry (DXA) has emerged as a new reference standard for body composition studies, replacing underwater weighing. While DXA scans have become a valued research tool, it is unclear how information regarding body composition could be used in the active medical management of the patient to alter treatment decisions or improve health outcomes. No studies have been identified in literature searches in which DXA body composition measurements were actively used in patient management, and studies have not reported data demonstrating the impact of body composition assessment on health outcomes. Therefore, the technique is considered investigational.

Practice Guidelines and Position Statements

In 2013, the International Society for Clinical Densitometry (ISCD) issued a statement on use of DXA for body composition.(11) The statement included the following ISCD official positions regarding use of DXA total body composition with regional analysis:

  • To assess fat distribution in patients with HIV who are using antiretroviral agents known to increase the risk of lipoatrophy. The statement noted that, although most patients who were taking medications known to be associated with lipoatrophy switched to other medications, some remain on these medications and DXA may be useful in this population to detect changes in peripheral fat before they become clinically evident.
  • To assess fat and lean mass changes in obese patients undergoing bariatric surgery when weight loss exceeds approximately 10%. The statement noted that the impact of DXA studies on clinical outcomes in these patients is uncertain.
  • To assess fat and lean mass in patients with risk factors associated with sarcopenia, ie, with muscle weakness or poor physical functioning.

U.S. Preventive Services Task Force Recommendations

The U.S. Preventive Services Task Force (USPSTF) does not recommend DXA for body composition analysis. In 2012, USPSTF recommended screening all adults for obesity with BMI.(12) Its 2010 recommendation on obesity in children and adolescents recommends screening all children older than 6 years old using BMI.(13) As of November 2014, the 2010 recommendation is in the process of being updated.

Medicare National Coverage

There is no national coverage determination (NCD). In the absence of an NCD, coverage decisions are left to the discretion of local Medicare carriers.

References:

  1. Alves FD, Souza GC, Biolo A, et al. Comparison of two bioelectrical impedance devices and dual-energy X-ray absorptiometry to evaluate body composition in heart failure. J Hum Nutr Diet. Mar 29 2014. PMID 24684316
  2. Ziai S, Coriati A, Chabot K, et al. Agreement of bioelectric impedance analysis and dual-energy X-ray absorptiometry for body composition evaluation in adults with cystic fibrosis. J Cyst Fibros. Sep 2014;13(5):585-588. PMID 24522087
  3. Elkan AC, Engvall IL, Tengstrand B, et al. Malnutrition in women with rheumatoid arthritis is not revealed by clinical anthropometrical measurements or nutritional evaluation tools. Eur J Clin Nutr. Oct 2008;62(10):1239-1247. PMID 17637600
  4. Jensky-Squires NE, Dieli-Conwright CM, Rossuello A, et al. Validity and reliability of body composition analysers in children and adults. Br J Nutr. Oct 2008;100(4):859-865. PMID 18346304
  5. Kullberg J, Brandberg J, Angelhed JE, et al. Whole-body adipose tissue analysis: comparison of MRI, CT and dual energy X-ray absorptiometry. Br J Radiol. Feb 2009;82(974):123-130. PMID 19168691
  6. Liem ET, De Lucia Rolfe E, L'Abee C, et al. Measuring abdominal adiposity in 6 to 7-year-old children. Eur J Clin Nutr. Jul 2009;63(7):835-841. PMID 19127281
  7. Bedogni G, Agosti F, De Col A, et al. Comparison of dual-energy X-ray absorptiometry, air displacement plethysmography and bioelectrical impedance analysis for the assessment of body composition in morbidly obese women. Eur J Clin Nutr. Nov 2013;67(11):1129-1132. PMID 24022260
  8. Monteiro PA, Antunes Bde M, Silveira LS, et al. Body composition variables as predictors of NAFLD by ultrasound in obese children and adolescents. BMC Pediatr. 2014;14:25. PMID 24476029
  9. Bazzocchi A, Ponti F, Cariani S, et al. Visceral Fat and Body Composition Changes in a Female Population After RYGBP: a Two-Year Follow-Up by DXA. Obes Surg. Sep 14 2014. PMID 25218013
  10. Franzoni E, Ciccarese F, Di Pietro E, et al. Follow-up of bone mineral density and body composition in adolescents with restrictive anorexia nervosa: role of dual-energy X-ray absorptiometry. Eur J Clin Nutr. Feb 2014;68(2):247-252. PMID 24346474
  11. Kendler DL, Borges JL, Fielding RA, et al. The Official Positions of the International Society for Clinical Densitometry: Indications of Use and Reporting of DXA for Body Composition. J Clin Densitom. Sep 30 2013. PMID 24090645
  12. U.S. Preventive Services Task Force (USPSTF). Screening for Obesity in Adults. http://www.uspreventiveservicestaskforce.org/3rduspstf/obesity/obesrr.htm. Accessed November 1, 2014.
  13. U.S. Preventive Services Task Force (USPSTF). Obesity in Children and Adolescents: Screening. http://www.uspreventiveservicestaskforce.org/Page/Topic/recommendation-summary/obesity-in-children-and-adolescents-screening?ds=1&s=obesity in children. Accessed November 1, 2014.

Codes

Number

Description

CPT 76499 Unlisted diagnostic radiographic procedure
ICD-9 Diagnosis   Investigational for all diagnoses
ICD-10-CM (effective 10/1/15)   Investigational for all diagnoses
ICD-10-PCS (effective 10/1/15)   ICD-10-PCS codes are only used for inpatient services. There is no specific ICD-10-PCS code for this imaging.
  BW0KZZZ, BW0LZZZ Imaging, anatomical regions, plain radiography, codes for whole body or whole skeleton

Index
Body Composition, DEXA
Body Composition, DXA
DEXA, Body Composition
DXA, Body Composition
Whole Body Dual X-Ray Absorptiometry
Dual-Energy X-Ray Absorbtiometry

Policy History

Date Action Reason
07/17/03 Add policy to Radiology section New policy
11/9/04 Replace policy Policy updated with literature review; policy statement unchanged
08/17/05 Replace policy Policy updated with literature review; policy statement unchanged
02/15/07 Replace policy Policy updated with literature review; reference numbers 12 to 15 added; policy statement unchanged
06/12/08 Replace policy Policy updated with literature review; reference numbers 16-18 added; policy statement unchanged
12/11/08 Replace policy - coding update only CPT coding updated
02/11/10 Replace policy Policy updated with literature review; reference numbers 19-23 added; policy statement unchanged
12/9/10 Replace policy - coding update only ICD-10 codes added to policy.
03/10/11 Replace policy Policy updated with literature review, rationale section extensively edited, some references renumbered or removed, no changes in policy statement
12/08/11 Replace policy Policy updated with literature review through October 2011, references added and reordered, policy statement unchanged
12/13/12 Repalce Policy
Policy updated with literature review through October 2012. No new references added. Policy statement unchanged
12/12/13 Replace policy Policy updated with literature review through October 25, 2013. References 25 and 27 added. Policy statement unchanged.
12/11/14 Replace policy Policy updated with literature review through October 15, 2014. References 1-2, 7-9, and 12-13 added. Policy statement unchanged.