Medical Policy: 06.01.31
Original Effective Date: September 2013
Reviewed: April 2019
Revised: April 2016
This policy contains information which is clinical in nature. The policy is not medical advice. The information in this policy is used by Wellmark to make determinations whether medical treatment is covered under the terms of a Wellmark member's health benefit plan. Physicians and other health care providers are responsible for medical advice and treatment. If you have specific health care needs, you should consult an appropriate health care professional. If you would like to request an accessible version of this document, please contact customer service at 800-524-9242.
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This Medical Policy document describes the status of medical technology at the time the document was developed. Since that time, new technology may have emerged or new medical literature may have been published. This Medical Policy will be reviewed regularly and be updated as scientific and medical literature becomes available.
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 AIDS or post bariatric surgery. A variety of measurement methods have been researched, including most commonly, anthropomorphic measures, bioelectrical impedance, dual x-ray absorptiometry (DXA), and underwater weighing and imaging. All of these methods 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). There has been an interest in using whole body dual x-ray absorptiometry (DXA) and bioelectrical impedance analysis (BIA) in the clinical care setting rather than a research setting.
Routinely, anthropomorphic measures are sufficient to estimate adiposity in a clinical setting. Anthropometric measurements include the following:
The measurement sites vary depending on the specific skinfold testing protocol being used, but typically include the following seven locations on the body:
According to the American College of Sports Medicine, when performed by a trained, skilled tester, skinfold measurements of body fat are up to 98% accurate. However, due to new technologies available such as electrical impedance methods and scales that measure body composition instead of directly measuring skinfolds, skinfold testing may not be utilized like it once was in clinical practice setting.
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. While valued as a research tool, weighing people underwater 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 (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. In addition, the density of body fat may vary, depending on the relative components of its constituents (eg, glycerides, sterols, glycolipids).
Magnetic resonance imaging (MRI) or computed tomography (CT) can be used to measure visceral adipose tissue. The technique usually quantifies adipose tissue in a single slice cross section at the level of the L4/L5 lumbar disc. The subcutaneous fat (outside the abdominal musculature) may be measured in the same image. These measures of visceral adiposity correlate with insulin resistance, triglycerides, hepatic steatosis, and other components of the metabolic syndrome. This technique is used for research in obesity and metabolic disease, and does not contribute to clinical care.
Bioelectrical impedance is based on the relationship 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. 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.
Using low dose x-rays different energy levels, whole body dual x-ray absorptiometry (DXA) measure lean tissue mass, total and regional body fat, as well as bone density. DXA scans have become a tool for research body composition, but there has been an interest in using DXA in the clinical care setting rather than a research setting.
While the cited techniques above 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 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 has the ability to determine body composition in defined regions (i.e. 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 be variable in certain disease states. Other assumptions used to derive body composition estimates are considered proprietary by DXA manufacturers.
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. 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 Alves et. al. compared 2 bioelectrical impedance devices with DXA for the evaluation of body composition in heart failure. Another 2014 study Ziai et. al. compared bioelectrical impedance analysis with DXA for evaluating body composition in adults with cystic fibrosis. Whether or not 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 versus 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.
The ability to detect a 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 bone mineral density (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.
For individuals who have a clinical condition associated with abnormal body composition who receive DXA body composition studies, the evidence includes several cross-sectional studies comparing DXA with other techniques. The available studies were primarily conducted in research settings and often used 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 net 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. 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 net health outcomes.
Bioelectrical impedance analysis (BIA) measurement is simple and widely used but has limitations. Impedance is measured by applying electrodes to one arm and one leg or by standing on 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. BIA is influenced by sex, age, disease state, and level of fatness (because total body water and relative extracellular water are greater in obese individuals). The data suggest that BIA results are not as accurate no matter which formula is used to do the calculation and remains problematic in its ability to assess percent body fat, fat mass or fat-free mass.
Based on review of the peer reviewed medical literature, there is currently no established role for whole body bioelectrical impedance analysis (BIA) 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. Currently no studies have been identified in the literature in which BIAmeasurements were actively used in patient management, and studies have not reported data demonstrating the impact of body composition assessment on net health outcomes. Further studies are needed to assess the clinical value of this testing.
In 2015, The International Society for Clinical Densitometry (ISCD) updated thier adult position statement which included a statement on the use of DXA body composition. The statement included the following ISCD position regarding the use of DXA total body composition with regional analysis in the following condtions:
The position statement also included, pregnancy is a contraindication to DXA body composition.
In 2012, the USPSTF recommends screening all adults for obesity. Clinicians should offer or refer all patients with body mass index (BMI) of 30 kg/m2 or higher to intensive, multicomponent behavioral interventions.
Body mass index is calculated from the measured weight and height for an individual. Recent evidence suggests that waist circumference may be an acceptable alternative to BMI measurement in some patient subpopulations. In 2003, The USPSTF found adequate evidence that BMI is an acceptable measure for identifying adults with excess weight.
In 2017, the USPSTF recommends that clinicians screen for obesity in children and adolescents 6 years and older and offer or refer them to comprehensive, intensive behavioral interventions to promote improvements in weight status.
Body mass index measurement is the recommended screening test for obesity. Body mass index percentile is plotted on growth charts, such as those developed by the CDC, which are based on US-specific, population-based norms for children 2 years and older. Obesity is defined as an age- and sex-specific BMI in the 95th percentile or greater.
In 2013, the ACC/AHA/TOS issued a guideline for the management of overweight and obesity in adults and the summary of recommendations for obesity state, “identifying patients who need to lose weight (BMI and waist circumference), measure height and weight and calculate BMI at annual visits or more frequently. Measure weight circumference at annual visits or more frequently in overweight and obese adults.” (E-Expert Opinion)
This guideline mentions no role of whole body dual x-ray absorptiometry (DXA) or bioelectrical impedance analysis (BIA) in the assessment and management of overweight and obese adults.
In 2014, National Institute for Health and Clinical Excellence (NICE) issued a guideline on obesity: identification, assessment and management. The guideline included the following:
Dual x-ray absorptiometry (DXA) and whole body bioelectrical impedance analysis (BIA) for body composition studies is considered investigational for all indications.
Based on review of the peer reviewed medical literature there is insufficient evidence to support the use of whole body dual x-ray absorptiometry (DXA) and whole body bioelectrical impedance analysis (BIA) for the purpose of determining body composition. 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. Well-designed studies evaluating the diagnostic accuracy and clinical utility of this testing are lacking. Further studies are needed to assess the clinical value of this testing. The evidence is insufficient to determine the effects of the technology on net health outcomes.
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