Ms. Falcon is an exercise science intern in the Physical Medicine & Rehabilitation Service, and Dr. Harris-Love is the associate director of the Human Performance Research Unit in the Clinical Research Center, both at the Washington DC VAMC. Dr. Harris-Love also is an associate clinical professor at the George Washington University Milken Institute School of Public Health, and Ms. Falcon is a program coordinator with the Children’s National Health System, both in Washington DC.
Author disclosures The authors report no actual or potential conflicts of interest with regard to this article.
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Staging criteria are generally used to denote the severity of a given disease or syndrome, whereas classification criteria are used to define homogenous patient groups based on specific pathologic or clinical features of a disorder. Although classification schemes may incorporate an element of severity, they are primarily used to characterize fairly distinct phenotypic forms of disease or specific clinical presentation patterns associated with a well-defined syndrome. Although not universally adopted, the European consensus group sarcopenia staging criteria are increasingly used to provide a staging algorithm presumably driven by the severity of the condition. 19
The assessment of functional performance for use in sarcopenia staging often involves measuring habitual gait speed or completing the Short Physical Performance Battery (SPPB). 23 The SPPB involves a variety of performance-based activities for balance, gait, strength, and endurance. This test has predictive validity for the onset of disability and adverse health events, and it has been extensively used in research and clinical settings. 33 Additional tests used to characterize function during the staging or diagnostic process include the timed get up and go test (TGUG) and the timed sit to stand test. 34,35 The TGUG provides an estimate of dynamic balance, and the sit to stand test has been used as very basic proxy measure of muscular power. 36 The sit to stand test and habitual gait speed are items included in the SPPB. 33
Accepted methods to obtain the traditional index measure of sarcopenia—based on estimates of LBM—include bioimpedance analysis (BIA) and dual X-ray absorptiometry (DXA). The BIA uses the electrical impedance of body tissues and its 2 components, resistance and reactance, to derive its body composition estimates. 37 Segmental BIA allows for isolated measurements of the limbs, which may be calibrated to DXA appendicular lean body mass (ALM) or magnetic resonance imaging-based estimates of LBM. This instrument is relatively safe for use, inexpensive for medical facilities, and useful for longitudinal studies, but it can be confounded by issues, such as varying levels of hydration, which may affect measurement validity in some instances.
Despite the precision of DXA for estimating densities for whole body composition analysis, the equipment is not very portable and involves low levels of radiation exposure, which limits its utility in some clinical settings. While each body composition assessment method has its advantages and disadvantages, DXA is regarded as an acceptable form of measurement for hospital settings, and BIA is frequently used in outpatient clinics and community settings. Other methods used to estimate LBM with greater accuracy, such as peripheral quantitative computed tomography, doubly labeled water, and whole body gamma ray counting, are not viable for clinical use. Other accessible methods such as anthropometric measures and skinfold measures have not been embraced by sarcopenia classification consensus groups. 23,37
Alternative methods of estimating LBM, such as diagnostic ultrasound and multifrequency electrical impedance myography, are featured outcomes in ongoing clinical trials that involve veteran participants. These modalities may soon provide a clinically viable approach to assessing muscle quality via estimates of muscle tissue composition. 37,38 Similar to the management of other geriatric syndromes, interprofessional collaboration provides an optimal approach to the assessment of sarcopenia. Physicians and other health care providers may draw on the standardized assessment of strength and function (via the SPPB and hand-grip dynamometry) by physical therapists (PTs), questionnaires administered by nursing staff (the SARC-F), or body composition estimates from other health professionals (ranging from BIA to DXA) to aid the diagnostic process and facilitate appropriate case management (Table 2).
