Medical Policies - Radiology
Whole Body Composition Analysis using Dual X-Ray Absorptiometry (DXA) or Bioelectrical Impedance Analysis (BIA)
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Whole body composition analysis using dual X-Ray absorptiometry (DXA) or bioelectrical impedance analysis (BIA) is considered experimental, investigational and/or unproven.
Body Composition Measurement
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 occur with acquired immune deficiency syndrome or after bariatric surgery. A variety of techniques have been researched, including most commonly, anthropomorphic measures, bioelectrical impedance, and dual x-ray absorptiometry (DXA). 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 (i.e., different age groups, ethnicities, or underlying conditions). Techniques using anthropomorphics, bioelectrical impedance, underwater weighing, and DXA are briefly reviewed as followed.
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 gender.
Bioelectrical impedance is based on the relation among 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. 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 (UWW) 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. 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 (i.e., 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 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 also can determine body composition in defined regions (i.e., 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.
Body composition software for several bone densitometer systems have been approved by the U.S. Food and Drug Administration through the premarket approval process. They include the Lunar iDXA systems (GE Healthcare, Madison, WI), Hologic DXA systems (Hologic, Bedford MA), and Norland DXA systems (Norland, at Swissray, Fort Atkinson, WI).
This medical policy was originally created in April 2005 and has been updated regularly with searches of scientific literature through May 2018. The key literature is described below.
Dual X-Ray Absorptiometry as a Diagnostic Test to Detect Abnormal Body Composition
Most of the literature on dual x-ray absorptiometry (DXA) as a diagnostic test to detect abnormal body composition involves the use of the technology in the research setting, often as a reference test; studies have been conducted in different populations of patients and underlying disorders. (1-9) In some cases, studies have compared 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, a 2014 study 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) Whether or not 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 and improve health outcomes.
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 (i.e., bone, fat, lean mass) for different populations of patients at different ages. Regarding measuring bone mineral density (BMD), normative databases have largely focused on postmenopausal white women, and these values cannot necessarily be extrapolated to 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 reported on DXA measurement of body composition changes over time in clinical populations; none of these studies used DXA findings to make patient management decisions or addressed how serial body composition assessment might improve health outcomes. (10, 11) For example, in 2014, Franzoni et al. published a prospective study evaluating body composition in adolescent females with restrictive anorexia nervosa. (11) Patients underwent DXA at baseline and 12 months after treatment for their eating disorder. A total of 46 (58%) of 79 patients 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 correlated significantly with change in BMI.
Bioelectrical impedance has been identified as an emerging technique to assess body composition in the obese population and other conditions. (12, 13) However, the limited literature does not demonstrate the impact this testing may have on meaningful clinical outcomes.
In a systematic review published by Haverkort et al. (2015) the authors aim was to explore the variability of empirical prediction equations used in bioelectrical impedance analysis (BIA) estimations and to evaluate the validity of bioelectrical impedance estimations in adult surgical and oncological patients. (14) Studies developing new empirical prediction equations and studies evaluating the validity of BIA estimations compared with a reference method were included. Only studies using BIA devices measuring the entire body were included. To illustrate variability between equations, fixed normal reference values of resistance values were entered into the existing empirical prediction equations of the included studies. The validity was expressed by the difference in means between BIA estimates and the reference method, and relative difference in %. Substantial variability between equations for groups was found for total body water (TBW) and fat free mass (FFM). BIA mainly under-estimated TBW (range relative difference -18.8 % to +7.2 %) and FFM (range relative differences -15.2 % to +3.8 %). Estimates of the FM demonstrated large variability (range relative difference -15.7 % to +43.1 %). The authors concluded that application of equations validated in healthy subjects to predict body composition performs less well in oncologic and surgical patients. It was suggested that BIA estimations can only be useful when performed longitudinally and under the same standard conditions.
In an UpToDate (2016) publication titled “Determining body composition in Adults” (15) the authors note that dual-energy x-ray absorptiometry (DXA) is one of the more commonly used methods for determining body composition. This method is based on the attenuation of signals from two energy sources to provide a three-compartment model of body composition. In a study comparing DXA with a four-compartment model of body composition, estimates of mean percent body fat were similar between the two methods. However, there was considerable intraindividual variability, ranging from -3.0 to +4.0 percent, with DXA. Thus, DXA is good for cross-sectional measurements, but is less reliable for individual measures. In addition, impedance measurement is widely used but has limitations. Impedance is measured by applying electrodes to one arm and one leg or by standing on the foot plates of a special scale. Impedance is proportional to the length of the conductor and inversely related to the cross-sectional area of the conductor. Accuracy in placement of electrodes is essential because variations can cause relatively large errors in the measurement of impedance and corresponding errors in the estimate of body water. A variety of formulas have been developed to convert impedance, which measures body water, into an estimate of fat. Most formulas for estimating fat from bioelectric impedance analysis underestimate body fat. As an example, in a study comparing two bioelectric impedance devices with DXA for the measurement of body fat, percent body fat measured with both bioelectric impedance devices were 2 to 6 percent lower in men and women with normal BMI. Among the overweight individuals, the values were lower in women but similar in men. In the summary of this article the authors note that if there is concern about whether fat is increased, particularly visceral fat, dual-energy x-ray absorptiometry (DXA) may be beneficial. Although impedance measurements are used in many clinical settings, they do not contribute more than the other methods outlined in the publication.
Ongoing and Unpublished Clinical Trials
A search of ClinicalTrials.gov in August 2017 did not identify any ongoing or unpublished trials that would likely influence this review.
Summary of Evidence
For individuals who have a clinical condition associated with abnormal body composition who receive dual x-ray absorptiometry (DXA) body composition studies, the evidence includes several cross-sectional studies comparing DXA with other techniques. Relevant outcomes are symptoms and change in disease status. The available studies were primarily conducted in research settings and often use DXA body composition studies as a reference standard; these studies do not permit conclusions about the accuracy of DXA for measuring body composition. More importantly, no studies were identified in which DXA body composition measurements were actively used in patient management. The evidence is insufficient to determine the effects of the technology on health outcomes.
For individuals who have a clinical condition managed by monitoring changes in body composition over time who receive DXA body composition studies, the evidence includes several prospective studies monitoring patients over time. Relevant outcomes are symptoms and change in disease status. The studies used DXA as a tool to measure body composition and were not designed to assess the accuracy of DXA. None of the studies used DXA findings to make patient management decisions or addressed how serial body composition assessment might improve health outcomes. The evidence is insufficient to determine the effects of the technology on health outcomes.
For individuals who have a clinical condition associated with abnormal body composition or who have a clinical condition managed by monitoring changes in body composition over time who receive bioelectrical impedance analysis, the evidence includes peer reviewed literature that does not establish its accuracy. Studies evaluating the diagnostic accuracy and clinical utility are lacking. The evidence is insufficient to determine the effects of the technology on health outcomes.
Practice Guidelines and Position Statements
International Society for Clinical Densitometry (ISCD)
In 2013, the ISCD issued statements on the use of DXA total body composition. (16) The following statements were made on the 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, including muscle weakness and poor physical functioning.
National Institute for Health and Care Excellence (NICE)
NICE published a clinical guideline regarding obesity: identification, assessment and management in 2006, amended in 2014. The recommendations for adults and children do not use bioimpedance as a substitute for body mass index (BMI) as a measure of general adiposity. (17)
American Association of Clinical Endocrinologists (AACE) and American College of Endocrinology (ACE)
In 2016, the AACE and ACE published clinical practice guidelines for comprehensive medical care of patients with obesity. In the executive summary of the clinical practice guidelines the question was asked, what are the best anthropomorphic criteria for defining excess adiposity in the diagnosis of overweight and obesity in the clinical setting? (18) The following recommendations were made:
• “BMI should be used to confirm an excessive degree of adiposity and to classify individuals as having overweight (BMI 25-29.9 kg/m2) or obesity (BMI ≥30 kg/m2), after taking into account age, gender, ethnicity, fluid status, and muscularity; therefore, clinical evaluation and judgment must be used when BMI is employed as the anthropometric indicator of excess adiposity, particularly in athletes and those with sarcopenia (Grade A; BEL 2, upgraded due to high relevance).
• Other measurements of adiposity (e.g., bioelectric impedance, air/water displacement plethysmography, or dual-energy x-ray absorptiometry) may be considered at the clinician’s discretion if BMI and physical examination results are equivocal or require further evaluation (Grade C, BEL 2, downgraded due to evidence gaps). However, the clinical utility of these measures is limited by availability, cost, and lack of outcomes data for validated cutoff points (Grade B; BEL 2).”
The best evidence level (BEL) is accompanied by a recommendation grade (A, B, C, or D). This recommendation grade maps to the BEL and can be adjusted upward or downward by 1 level. Final recommendation grades may be interpreted as being based on strong (Grade A), intermediate (Grade B), weak (Grade C), or no (Grade D) scientific substantiation.
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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. Dec 2014; 27(6):632-638. 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. Jan 29 2014; 14:25. PMID 24476029
9. Tompuri TT, Lakka TA, Hakulinen M, et al. Assessment of body composition by dual-energy X-ray absorptiometry, bioimpedance analysis and anthropometrics in children: the Physical Activity and Nutrition in Children study. Clin Physiol Funct Imaging. Jan 2015; 35(1):21-33. PMID 24325400
10. 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. Mar 2015. PMID 25218013
11. 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
12. Lee S, Gallagher, D. Assessment methods in human body composition. Curr Opin Clin Nutr Meta Care. 2008 September; 11(5): 566–572. PMID 18685451
13. Switzer N, Mangat H, Karmali, S. Current trends in obesity: body composition assessment, weight regulation, and emerging techniques in managing severe obesity. Interv Gastroenterol. Jan 2013; 3(1):34-36.
14. Haverkort EB, Reijven PL, Binnekade JM, et al. Bioelectrical impedance analysis to estimate body composition in surgical and oncological patients: a systematic review. Eur J Clin Nutr. Jan 2015; 69(1):3-13. PMID 25271012
15. Bray, George UpToDate Determining body composition in adults. In: UpToDate, Post TW (Ed), Topic last updated: Apr 17, 2015. Accessed on March 21, 2016
16. 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. Oct-Dec 2013; 16(4):496-507. PMID 24090645
17. NICE – Obesity: identification, assessment and management (2014). Clinical guideline – CG189. National Institute for Health and Care Excellence (2018). Available at <https://www.nice.org.uk> (accessed - 2018 May 22).
18. Garvey WT, Mechanick JI, Brett EM, et al. American Association of Clinical Endocrinologists and American College of Endocrinology Comprehensive Clinical Practice Guidelines for medical Care of Patients with Obesity Executive Summary. Endocr Pract. Jul 2016; 22(7):842-884. PMID 27472012
19. Whole Body Dual X-Ray Absorptiometry to Determine Body Composition. Chicago, Illinois: Blue Cross Blue Shield Association Medical Policy Reference Manual (2017 September) Radiology 6.01.40.
|7/1/2018||Document updated with literature review. Coverage unchanged. References 14 and 17-18 added.|
|3/1/2017||Reviewed. No changes.|
|4/15/2016||Document updated with literature review. Coverage unchanged.|
|6/1/2015||Reviewed. No changes.|
|7/1/2014||Document updated with literature review. Whole body composition analysis using bioelectrical impedance was added to the experimental, investigational and/or unproven coverage statement. Title changed from: Whole Body Composition Analysis using Dual X-Ray Absorptiometry (DEXA). CPT/HCPCS code(s) updated.|
|10/15/2013||Document updated with literature review. Coverage unchanged.|
|6/1/2008||Policy reviewed without literature review; new review date only.|
|8/15/2007||Revised/updated entire document|
|4/1/2005||New medical document|
|Title:||Effective Date:||End Date:|
|Whole Body Composition Analysis using Dual X-Ray Absorptiometry (DXA) or Bioelectrical Impedance Analysis (BIA)||03-01-2017||06-30-2018|
|Whole Body Composition Analysis using Dual X-Ray Absorptiometry (DXA) or Bioelectrical Impedance Analysis (BIA)||04-15-2016||02-28-2017|
|Whole Body Composition Analysis using Dual X-Ray Absorptiometry (DEXA) or Bioelectrical Impedance Analysis (BIA)||06-01-2015||04-14-2016|
|Whole Body Composition Analysis using Dual X-Ray Absorptiometry (DEXA) or Bioelectrical Impedance Analysis (BIA)||07-01-2014||05-31-2015|
|Whole Body Dual X-Ray Absorptiometry (DEXA) to Determine Body Composition||10-15-2013||06-30-2014|
|Whole Body Dual X-Ray Absorptiometry (DEXA) to Determine Body Composition||06-01-2008||10-14-2013|
|Whole Body Dual X-Ray Absorptiometry (DEXA) to Determine Body Composition||08-15-2007||05-31-2008|
|Whole Body Dual X-Ray Absorptiometry (DEXA) to Determine Body Composition||04-01-2005||08-14-2007|