Sarcopenia Assessment Techniques

Abstract

Content available: Audio Recording Sarcopenia is a condition defined by loss of muscle strength, quantity, or function. It is characterized as muscle strength below the standard healthy adult mean, with physical performance considered an outcome measure.1, 2 Sarcopenia is common in the aging population, those with a sedentary lifestyle, and those with suboptimal nutrition intake or absorption. It is common in chronic diseases, such as cirrhosis, and is associated with a greater likelihood of adverse outcomes.1, 3 Suspected causes of sarcopenia in cirrhosis include hormonal and chemical alterations, endotoxins, ascites, decreased mobility, and decreased nutritional intake. Patients with cirrhosis with sarcopenia have decreased mobility, which impairs their participation in activities of daily living. There is also a greater risk for mortality in this population due to increased risk for falls.1, 3, 4 Measuring parameters of muscle mass and quality can be challenging and is often reserved for research purposes.2 Lean body mass (LBM) imaging, anthropometric measurement techniques (mid upper arm circumference [MUAC]), and muscle strength assessments together make up the gold standard of sarcopenia assessment.5 Multiple tools, variable in cost and availability, exist to assess LBM. The most common techniques include magnetic resonance imaging (MRI), computed tomography (CT), bioimpedance analysis (BIA), and dual-energy X-ray absorptiometry (DXA).6-8 MRI and CT are readily available methods for measuring skeletal muscle mass in patients with cirrhosis and are less prone to variability with volume status, as is common in patients with cirrhosis.7 The BIA measurement takes into account total body water when estimating muscle mass, and therefore can lack accuracy in patients with cirrhosis and volume overload.6 Although not as commonly available in clinical settings, DXA is able to distinguish between fat, bone, and muscle.5 See Tables 1 and 2 for further details regarding each technique. Anthropometry can also be used to evaluate LBM in sarcopenia. MUAC, skin-fold thickness, and calf circumference can predict overall muscle mass.8, 9 See Table 3 for details on how to perform these tests, as well as interpretation. MUAC measurement is thought to be closely related to overall body protein reserves.10 Skin-fold thickness is considered a proxy for body fat estimation.8, 9, 11 Calf circumference additionally has been proven to predict both performance and survival, making it the most reliable anthropometric measure.12, 13 Despite the relative ease of measuring anthropometry, it is not necessarily a strong measure of muscle mass. Potential for human error, skin elasticity alterations, changes in body mass related to aging, and differences in user techniques make this form of assessment less reliable.2, 5, 14 See Table 3 for how to perform and interpret measurement techniques. A variety of validated tools exist for muscle strength measurement, including handgrip strength and the chair stand test.2, 9 Handgrip strength is measured via a dynamometer and has been shown to closely correlate with lower-extremity strength.2, 15 The chair stand test acts as a proxy for quadriceps strength by measuring the time needed for a patient to rise from a seated position five times. Alternatively, a variation called the timed chair stand test counts the number of times a patient can rise from being seated over 30 seconds.2, 16-18 See Table 4 for how to perform and interpret testing. Multiple validated tests are available to measure physical performance. These include the Stair Climb Power Test (SCPT), Timed Get Up-and-Go (TGUG) test, and the Short Physical Performance Battery (SPPB). The SCPT is a simple way to measure a patient’s leg power by having the patient climb a flight of stairs.5, 19, 20 Although clinically feasible and inexpensive due to ease of use and the availability of stairs in most facilities, it may be difficult for vulnerable, deconditioned patients.19 The TGUG measures a patient’s muscle performance by speed.5 The SPPB measures lower-extremity function by assessing a patient’s walking gait, balance, and chair stand.21 See Table 4 for how to perform and interpret testing. The European Working Group on Sarcopenia in Older People outlined a simple tool to identify people with sarcopenia2 using just three criteria: low muscle strength, low muscle quantity or quality, and low physical performance. The 2018 definition uses low muscle strength as the primary parameter with probably sarcopenia if present. Sarcopenia is confirmed if both low muscle strength and low muscle quantity or quality are present. Sarcopenia is classified as severe if all three are present. LBM imaging, anthropometric measurement techniques, and muscle strength assessments together can adequately assess for loss of muscle strength, muscle quantity, and muscle function. All three categorical assessments together make up the gold standard of sarcopenia assessment.

Topics & Concepts