Research progress on evaluation methods for skeletal muscle mass assessment in sarcopenia (Review)

Introduction

Sarcopenia is an age-related syndrome characterized by a progressive and generalized loss of skeletal muscle mass, strength and function. It is associated with various adverse clinical outcomes, including fracture, falls and mortality (1–3). Sarcopenia is particularly prevalent among elderly patients with cancer (4,5) and can occur across all types of cancer. Studies indicate that cancer patients with low skeletal muscle mass during treatment face increased risks of mortality, cancer recurrence and lower quality of life (6–8). A systematic meta-analysis of 39 studies involving 8,966 cancer patients revealed an overall pooled sarcopenia prevalence of 42% [95% confidence interval (CI) 0.36–0.48; P<0.001], with substantial heterogeneity across cancer subtypes (8). Consistent with these findings, a review revealed a particularly high prevalence of sarcopenia (approaching 70%) in patients with esophageal, gastrointestinal, lung, head and neck malignancies, compared with a moderate prevalence (~50%) in those with breast, renal cell and hematologic cancers (9). These tumor-specific prevalence patterns exhibited correlations with disease stage, progression kinetics and the severity of nutritional and absorptive dysfunction. Although the pathogenesis of sarcopenia is not well understood, early identification of at-risk patients and timely intervention can markedly reduce the risk of adverse clinical outcomes.

The diagnosis of sarcopenia requires assessing muscle mass, muscle strength and physical performance (10). The assessment of muscle mass is a critical component in the clinical diagnosis of sarcopenia (1,11). Currently, the measurement of the cross-sectional area (CSA) of the third lumbar vertebra (L3) using computed tomography (CT) or magnetic resonance imaging (MRI) is considered a reliable method for assessing muscle mass. However, taking into account the expense, convenience, radiation exposure and equipment availability, various alternative methods have been developed, such as calf circumference (CC), mid-upper arm circumference and surrogate vertebral measurements. The present review summarized current methods for measuring skeletal muscle mass, aiming to early identify potential sarcopenia cases and facilitate timely intervention.

Methodology

Literature search strategy

A systematic literature search was performed across three principal databases: PubMed/Medline (https://pubmed.ncbi.nlm.nih.gov), Web of Science (https://webofscience.clarivate.cn) and China National Knowledge Infrastructure (CNKI, http://www.cnki.net), between January 2010 and February 2024. The search strategy used Medical Subject Headings (MeSH) terminology with Boolean operators, structured as follows:

Pathology Concepts: sarcopenia OR ‘skeletal muscle’ OR ‘muscle wasting’ OR ‘muscle atrophy’ OR ‘body composition’ OR ‘muscle mass’ OR ‘cachexia’ OR ‘muscle weakness’

Measuring Methods: ‘calf circumference (CC)’ OR ‘mid-arm muscle circumference (MAMC)’ OR ‘Yubi-wakka test’ OR ‘bioimpedance analysis (BIA)’ OR ‘computed tomography (CT)’ OR ‘magnetic resonance imaging (MRI)’ OR ‘dual-energy X-ray absorptiometry (DXA)’ OR ‘ultrasound (US)’

The search syntax employed Boolean AND operators between these two conceptual groups. The study selection workflow is schematically presented in Fig. 1.

Figure 1. PRISMA flow diagram of literature search and article selection. PRISMA, preferred reporting items for systematic reviews and meta-analyses.

Eligibility criteria

Eligible studies met the following criteria: Investigation of skeletal muscle mass assessment in sarcopenia populations, with particular emphasis on cancer patients or geriatric cohorts; employment of at least one validated measurement modality for muscle mass evaluation, including, but not limited to, anthropometric measurements, medical imaging techniques (CT/MRI/DXA), or BIA; and peer-reviewed original research articles published in English or Chinese.

Exclusion criteria

Studies were excluded based on the following considerations: Case reports, conference abstracts, commentaries, or non-peer-reviewed publications; articles lacking standardized diagnostic thresholds for low muscle mass determination; duplicate publications or studies with substantial cohort overlap.

Study selection and flowchart

The literature screening process followed the PRISMA guidelines (Fig. 1). Initial searches identified 5,036 records. After removing duplicates (n=1,343), 3,693 titles/abstracts were screened. Of these, 3,323 were excluded for irrelevance (non-sarcopenia or low muscle mass focus). A full-text review of 276 articles led to the exclusion of 142 studies (due to insufficient data or non-quantitative methods). Ultimately, 51 studies were included for the present review.

Data extraction

A total of two independent reviewers extracted data using a standardized form, including: Study characteristics (author, year, design); population (sample size, age, cancer type); muscle mass assessment methods and cut-off values.

Anthropometry

Calf circumference (CC)

CC serves as a straightforward and convenient indicator for assessing muscle mass, playing a crucial role in determining sarcopenia cut-off values (12–14). The Asian Working Group for Sarcopenia (AWGS) 2019 consensus updated the diagnosis criteria for sarcopenia and recommended CC as an effective screening tool in community (15–17). Compared with commonly used methods for assessing muscle mass, CC shows a positive association with muscle mass measured by BIA and DXA, regardless of age or body fat percentage (18). Özcan et al (19) reported a positive association between CC and low muscle mass in patients receiving maintenance hemodialysis. Numerous studies have investigated the relationship between CC and low muscle mass, establishing frequently utilized cut-off values of <34 cm for males and <33 cm for females, as detailed in Table I.

Table I. Summary of research on CC cut-off values for predicting low skeletal muscle mass.

Table I.

Summary of research on CC cut-off values for predicting low skeletal muscle mass.

First author/s, year	Population	Country/Region	Position	Comparing	Criteria for cut-off point	Cut-off for CC (cm)	(Refs.)
Champaiboon et al, 2023	6,404 older adults (≥60 years)	Thailand	Sitting	BIA	AWGS	♀<33, ♂<34 BMI ≥25:♀<34, ♂<35 older-old adults ≥75 years: ♀<33, ♂<34	(13)
Fernandes et al, 2022	796 older adults (≥60 years)	Southeast region of Brazil	Standing	GAMs	WHO (1995) Physical Status: The Use and Interpretation of Anthropometry. WHO technical report series; 854 Geneva, Switzerland	<34.5 (mortality)	(81)
Gonzalez et al, 2021	3,104 participants aged 18–39 years and with normal BMI (18.5–24.9)	US population	Siting	-	1 and 2 SDs below the mean	Moderately low values ♂ ≤34, ♀ ≤33 severely low CC values: ♂≤32, ♀≤ 31 adjusted BMI: adding 4 cm (BMI <18.5) or subtracting 3,7, or 12 cm (BMI 25–29, 30–39, and ≥40, respectively)	(12)
Xu et al, 2020	7,311 cases of Chinese elderly hospitalized population aged >70 years	China	Supine	-	GLIM Criteria	♂≤29.6, ♂≤27.5	(20)
Kawakami et al, 2020	1,239 adults ≥40 years	Japan	Standing	DEXA/BIA	AWGS	♂<35 (BIA)/36 (DXA), ♀<33 (BIA)/34 (DXA)	(18)
Kim et al, 2018	657 older aged (70–84 years)	Koreans	Standing	DXEA	AWGS	♂<35, ♀<33 in community-dwelling Korean elders	(64)
Pagotto et al, 2018	132 elderly people	Brazil	Standing	DEXA	LMM: ♂:7.26 kg/m2, ♀5.45 kg/m2	♂<34, ♀<33	(82)
Maeda et al, 2017	1,164 hospitalized, elderly adults	Japan	Supine	BIA	AWGS	♀≤ 29, ♂≤30	(83)
Barbosa-Silva et al, 2016	1,291 community-dwelling elderly aged 60 y or over	Brazil	Standing	DEXA	EWGSOP2	♂≤34, ♀≤33	(69)
Kawakami et al, 2015	40~89 y adults	Japan	Standing	DEXA	AWGS	♂<34, ♀<33	(84)

[i] CC, calf circumference; ♀, female; ♂, male; BIA, bioelectrical impedance analysis; BMI, body mass index; GAMs, generalized additive models; AWGS, Asian Working Group for Sarcopenia; LMM, low muscle mass; DEXA, Dual Energy X-Ray Absortometry; EWGSOP2, European Working Group on Sarcopenia in Older People 2.

Xu et al conducted two consecutive studies involving 7,311 hospitalized elderly patients aged >70 years in China, using a prospective multi-center database established by the authors. In the first study, the critical value of CC was determined using the receiver operating characteristic curve method, with in-hospital mortality as the primary outcome. This value was further validated using clinical and financial metrics. In the second study, three screening tools, NRS 2002, NA-SF and MUST, were employed for risk assessment. Malnutrition was diagnosed based on the GLIM criteria, incorporating the newly identified CC values. The optimal cut-off for CC was determined to be 29.6 cm for men and 27.5 cm for women (20).

The measurement of CC can be influenced by body type and positioning. Studies have shown that CC tends to be markedly higher in individuals with sedentary lifestyles (21). Furthermore, CC measurements vary across regions, populations and levels of physical activity intensity. These variations lead to differences in CC cut-off values for predicting low muscle mass. Therefore, it is essential to consider the effect of body type and positioning when measuring CC. Additionally, the most suitable criteria for sarcopenia screening using CC should be explored across diverse countries, regions and populations.

Mid-arm muscle circumference (MAMC)

A study assessed muscle mass in aging individuals using MAMC within the community, suggesting MAMC as a valid tool for evaluating nutrition and muscle mass in elderly adults (22). Carnevale et al (23) compared DXA and MAMC for muscle mass assessment, showing that MAMC is a practical screening tool for elderly patients and more effective in detecting low muscle mass. Gort-van Dijk et al (24) conclude that MAMC is more specific but less sensitive for assessing muscle mass. Despite these considerations, the convenience of MAMC makes it a recommended tool for screening decreased muscle mass in older populations (24). Notably, MAMC may be less suitable for subjects with edema (lymphedema or generalized extreme edema) or extreme obesity.

The cut-off values for determining low muscle mass using MAMC vary across studies and populations. Carnevale et al (23) established cut-off values of <11.0 cm for males and <10.3 cm for females in healthy young individuals. For older adults, the cut-offs were <22.3 cm for males and <18.6 cm for females. Gort-van Dijk et al (24) define low muscle mass as falling below the 10th percentile of MAMC cut-off values. However, there is no standardized cut-off value for MAMC to define low muscle mass. Further research is needed to establish its applicability across different age groups and to determine appropriate cut-off values.

Yubi-wakka (finger-ring) test

The finger-ring measurement (Yubi-wakka) is a self-testing tool developed by Tanaka et al (25) in 2018 to assess the risk of sarcopenia among community-dwelling older adults. Participants compared the circumference of their own hands with their CC. A larger CC indicated no sarcopenia risk, while equal measurements suggested potential early-stage sarcopenia. A smaller CC indicated sarcopenia risk necessitating further evaluation and intervention. Tanaka et al (25) verified the Yubi-wakka test in a study of 1,904 older adults (≥65 years), finding 53% in the larger CC group, 33% in the equal group and 14% in the smaller CC group. Multiple-factor analysis revealed that, compared with the larger CC group, the equal and smaller CC groups were more likely to develop sarcopenia (OR=2.4, 95% CI 1.4–4.1; OR=6.6, 95% CI 3.5–13, respectively). Lawongsa et al (26) replicated these findings in a study of Thai older adults, affirming the high sensitivity and specificity of the Yubi-wakka test for sarcopenia risk identification. At present, the Yubi-wakka test is primarily validated in Asian populations (27–29). Further research is needed to explore its applicability and validity across diverse ethnic groups.

Computed tomography (CT) and magnetic resonance imaging (MRI)

CT and MRI are widely used in clinical practice to assess muscle mass (30–32). CT can be targeted to show different body components by setting different thresholds, where the threshold for muscle tissue is −29~150 Hounsfield units (33,34). MRI relies on instrument-based marking or manual labeling of muscle tissue for accurate measurement (30). CT or MRI assessment of muscle mass usually involves measuring the skeletal muscle CSA from a single image. This value is then adjusted for height to calculate the skeletal muscle index (SMI, cm/m2) (35). Therefore, muscle mass measurements using CT or MRI require both the selection of experienced staff to circle the muscle area and, more importantly, the selection of appropriate and typical vertebrae to measure the CSA of the muscle. In addition to measuring skeletal muscle CSA for MRI, advanced MRI sequences can also enable the estimation of body composition in combination with the assessment of muscle mass abnormalities. This combined approach enhances the diagnostic accuracy of sarcopenia in aging patients (36). Xiao et al (35) show that CT-based diagnosis of sarcopenia can help to predict clinical outcomes and prognosis in surgical patients and illustrate that CT is intuitive, rapid and accurate in the diagnosis of sarcopenia. Beyond CSA measurement, CT can assess muscle steatosis by measuring intermuscular adipose tissue area or identifying muscle mass loss (37). Despite their advantages in sarcopenia diagnosis, CT and MRI are not widely used for screening due to their high cost, time consumption and ionizing radiation (in the case of CT) and the need for specialized technical expertise (35,36).

The third lumbar vertebra (L3)

The third lumbar vertebra (L3) is currently the most commonly used for measuring the SMI to assess whole-body muscle mass, given its strong correlation with whole-body musculature (r=0.86 ~0.94; P<0.001) (38). This method is considered the gold standard for diagnosis of low muscle mass and sarcopenia (39). Prado et al (40) measured the L3 SMI in patients with respiratory and gastrointestinal tumors to assess muscle mass. Martin et al (41) defined the cut-off value for sarcopenia as SMI <52.4 cm2/m2 in men and SMI <38.5 cm2/m2 in women. The L3 SMI cut-off values for assessing whole-body muscle mass range from 40.2–55.0 cm2/m2 in men and 30.0–43.23 cm2/m2 in women, respectively, as shown in Table II.

Table II. Summary of research on measuring muscle mass at L3 using computerized tomography.

Table II.

Summary of research on measuring muscle mass at L3 using computerized tomography.

First author/s, year	Population	Software	Criteria for cut-off point	Cutoff for Low SMI (cm2/m2)	(Refs.)
Sahin et al, 2023	162 stomach cancer patients, aged ≥18 years, Turkey	3D Slicer (version 4.10.2) (Slicer)	-	♂52.4; ♀38.5	(85)
Sealy et al, 2020	213 head and neck cancer patients, the Netherlands	Slice-O-Matic V5.0 (TomoVision)	Tertiles in the cohort	♂53.4; ♀43.23	(86)
Van der Kroft et al, 2020	180 patients with Colorectal cancer, Germany	Slice-O-Matic V5.0 (TomoVision)	At the lowest tertile	♂46.6; ♀36.8	(87)
Li et al, 2019	153 gastric cancer patients, China	Slice-O-Matic V5.0 (TomoVision)	Optimum stratification	♂40.2; ♀30.0	(88)
Blauwhoff-Buskermolen et al, 2017	241 cancer patients, aged ≥18 years, the Netherlands	Slice-O-Matic V5.0 (TomoVision)	-	♂55.0; ♀39.0	(89)

[i] L3, third lumbar vertebra.

By analyzing the relationship between SMI and prognosis in ovarian cancer patients, Jin et al (42) found significant variability in the cut-off values for low muscle mass among female patients. Commonly used SMI cut-off values ranged from 38.5–41.0 cm2/m2, with 38.5 and 41.5 cm2/m2 being the most frequently applied thresholds. The authors suggested that there was a large heterogeneity in the cut-off values for low muscle mass, potentially due to variations in methodology or population characteristics. As a clinical reference standard for assessing low SMI, the use of L3 needs further refinement to establish a robust diagnostic criterion. Considering that most of the patients do not routinely undergo CT scanning of the abdomen in clinical practice, performing such examinations solely for sarcopenia diagnosis would increase radiation exposure and assessment costs. In such case, researchers have tried to measure the CSA of other non-L3 vertebrae to evaluate muscle mass (43). Thus, it may be a cost-effective alternative measurement of skeletal muscle mass in screening of sarcopenia, improving patient prognosis without increasing additional economic and radiation burdens.

The third cervical vertebra (C3)

Patients with head and neck tumors have a higher risk of developing sarcopenia (44), but abdominal CT scanning is not routinely performed in this population. Thus, some researchers are exploring whether the C3 could serve as an alternative for screening low muscle mass in these patients. This approach could facilitate timely treatment, such as nutritional support or physical therapy and improve prognosis.

By measuring C3 and L3 muscle mass with CT in 51 trauma and 52 head and neck tumors patients, Swartz et al (44) found a strong correlation between L3 and C3 (r=0.891). The authors demonstrate that it is feasible to use the head and neck CT to evaluate muscle mass in head and neck tumors patients. This method also serves as a viable alternative to abdominal CT for measuring L3 muscle mass. Jung et al (45) also advocate the use of C3 CSA measured by head and neck CT to estimate L3 muscle mass in patients with head and neck tumors and predict overall survival. Meerkerk et al (30) used C3 muscle mass measurements to predict frailty in patients with head and neck tumors. The authors' findings showed that low SMI and sarcopenia are associated with frailty in older patients. Additionally, a retrospective cohort study has demonstrated a correlation between C3 muscle mass and prognosis in oral cancer patients, suggesting its potential as an imaging marker for predicting outcomes (46).

However, some researchers doubt whether the CSA measured by C3 can accurately predict the CSA of L3. Yoon et al (34) concluded that in patients with head and neck tumors complicated with sarcopenia, the muscle mass measured by C3 did not strongly correlate with that at L3 (r=0.381). This discrepancy is probably due to the fact that the sternocleidomastoid muscle at C3 was excluded from the analysis due to tumor invasion, leading to variability in the results between studies. Therefore, further research is needed to explore the feasibility of using C3 as a substitute for L3 in evaluating systemic muscle mass in patients' head and neck tumors. Key questions include how to measure C3 muscle mass, which muscles should be included and correlation between C3 and L3 muscle mass as well as the determination of a cut-off value for low muscle mass based on C3.

The fourth thoracic vertebra (Th4)

The Th4 is commonly used to assess muscle mass in patients undergoing chest CT scans for lung cancer and breast cancer. Gronberg et al (47) compared the concordance between Th4-measured SMI and L3-measured SMI and showed that there was only moderate concordance between them (r2=0.51 in men and r2=0.28 in women), indicating that Th4 cannot yet replace L3 to assess low muscle mass. Neefjes et al (48) also explored the use of Th4 for assessing low muscle mass and the findings suggested that further work is needed to validate the reliability of Th4 for this purpose. The current studies on the cut-off value of Th4 for assessing low muscle mass are summarized in Table III.

Table III. Summary of research on measuring muscle mass at Th4 using computerized tomography.

Table III.

Summary of research on measuring muscle mass at Th4 using computerized tomography.

First author/s, year	Population	Software	Criteria for cut-off point/muscle area	Cut-off for low SMI (cm2/m2)	(Refs.)
Tao et al, 2023	750 NSCLC patients, China	Simens syngo via VB20 (Siemens Healthineers)	X-tile software/bilateral pectoralis major, pectoralis minor muscles	♂ 18.1; ♀ 14.7	(90)
Sealy et al, 2020	213 head and neck cancer patients, the Netherlands	Slice-O-Matic V5.0 (TomoVision)	Tertiles in the cohort/Total muscle	♂69.45; ♀52.88	(86)
Van der Kroft et al, 2020	180 patients with Colorectal cancer, Germany	Slice-O-Matic V5.0 (TomoVision)	The lowest tertile/Total muscle	♂65.2; ♀51.9	(87)
Blauwhoff-Buskermolen et al, 2017	241 cancer patients, aged ≥18 years, the Netherlands	Slice-O-Matic V5.0 (TomoVision)	-/Total muscle	♂66.0; ♀51.9	(89)

[i] Th4, fourth thoracic vertebra; SMI, skeletal muscle index.

According to the current research results, the cut-off values of Th4 in evaluating low muscle mass and the muscle measurement area still are not standardized. Therefore, further research is needed for the adoption of Th4 instead of L3 to evaluate low muscle mass.

The twelfth thoracic vertebra (Th12)

Chest CT scans do not cover the L3 region, as that would increase both the financial burden and radiation exposure for patients who only need a chest CT. It is worth exploring how to diagnose sarcopenia without additional CT scans. Some researchers have attempted to use Th10, Th12 and other thoracic vertebrae for muscle mass assessment.

In a study by Matsuyama et al (49) Th12 muscle mass was measured using chest CT in patients with progressive oral squamous cell carcinoma. This value was compared with L3 muscle mass and the results showed that SMI measured at Th12 using chest CT can be used to diagnose sarcopenia and has predictive value for postoperative outcomes in these patients. In conclusion, current evidence is insufficient to support the use of Th10 and Th12 as alternatives to L3 for muscle mass measurement and more studies are needed.

Masticatory muscle

Masticatory muscles reflect the chewing and swallowing function of patients and are closely related to their nutritional status. Studies have shown that the mass of masticatory muscles is closely related to patients' grip strength, walking speed and physical activity (50,51). This suggests that masticatory muscles could serve as a new site for muscle mass measurement. Hwang et al (52) retrospectively analyzed 314 patients in emergency department and confirmed a significant association between masticatory muscle mass and systemic nutritional biomarkers. These findings suggest that masticatory muscle mass is a potential indicator of nutritional status, physical activity levels and trauma-related prognosis (53).

Chang et al (53) attempted to measure the muscle mass of the masticatory muscles in patients with head and neck cancers to explore its relationship with L3 muscle mass, specifically at the level of the mandibular notch. The authors found a strong correlation between masticatory muscle mass and L3 muscle mass (r=0.901). The study also suggested that C3 muscle mass measurements may be unreliable in patients with head and neck tumors involving lymphatic metastasis or severe muscle tissue invasion. Thus, measuring masticatory muscle mass might be a useful alternative. However, it should be noted that the number of studies on masticatory muscle for assessing low muscle mass is insufficient to support its validity as an alternative to L3.

Bilateral mid-thigh muscle area (TMA)

TMA has also been used to assess muscle mass. It provides more accurate evaluation of overall skeletal muscle mass and is highly sensitive to changes. The 2019 European Working Group on Sarcopenia in Older People (EWGSOP) guideline highlighted that mid-thigh muscle mass correlates more strongly with whole-body muscle mass than L1-L5 measurements (10). Tsai et al (54) found a strong correlation between TMA and abdominal muscle area (AMA) while investigating the relationship between lower extremity muscle mass and vascular stenosis in patients with peripheral arterial disease. This suggests that TMA could be another effective method for assessing muscle mass and future research in this area is warranted.

Clinical ultrasound (US)

US enables evaluation of muscle echotexture by detecting variations in intramuscular fat and connective tissue composition. Recently, the Sarcopenia Group of the European Geriatric Society published a consensus protocol for the detection of sarcopenia using ultrasound, including the measurements of CSA, muscle thickness, echo intensity, muscle wing angle and muscle bundle length (55). While the quadriceps remain the most studied muscle group, uncertainty persists regarding optimal anatomical measurement sites for assessing total skeletal muscle mass. Perkisas et al (56) concluded that muscle mass decreases before the number of muscle fibers is lost, which could be a reliable indicator of early signs of sarcopenia in the elderly. Although human errors in the interpretation of ultrasound results, might affect the formulation of unified diagnostic criteria, ultrasound still has the potential to become a tool for early screening and clinical diagnosis of sarcopenia due to its advantages of being non-invasive, painless, non-ionizing radiation and low-cost.

Dual energy X-ray absorptiometry (DXA)

DXA is currently widely used in body composition measurement due to its accuracy and repeatability. DXA enables simultaneous quantification of fat mass, appendicular skeletal muscle mass (ASM), fat-free mass (FFM) and bone mineral content. Studies demonstrate strong concordance between DXA-derived non-fat/adipose tissue measurements and corresponding values obtained via CT or MRI (1,57). ASMI measured by DXA varied in different study populations, with cut-off values ranging from 5.86 kg/m2−7.40 kg/m2 in males and from 4.42 kg/m2−5.67 kg/m2 in females (58). Based on available studies, EWGSOP2 has established the cut-off value for DXA to assess low muscle mass as ASMI <7.0 kg/m2 for males and <5.5 kg/m2 for females (59). The AWGS has established DXA cut-off values for assessing low muscle mass as ASMI <7.0 kg/m2 for males and <5.7 kg/m2 for females (60).

Nevertheless, DXA is unable to assess intramuscular fat infiltration (myosteatosis), which limits muscle quality evaluation. Furthermore, DXA measurements can be inaccurate due to variations in body thickness, fluid retention conditions (e.g., renal/hepatic dysfunction) and fluctuations in hydration status.

Bioimpedance analysis (BIA)

BIA is widely used for body composition assessment, indirectly calculating muscle mass using specific formulas. Cheng et al (57) demonstrated that BIA initially overestimates muscle mass but aligns closely with DXA measurements after adjustment, making it a rapid and reliable tool for sarcopenia screening. Compared with DXA, BIA is a simple measurement method with the advantages of being non-invasive, radiation-free and fast, making it an improved better choice for muscle mass screening of sarcopenia.

Although the AWGS2019 diagnostic criteria for sarcopenia define low muscle mass as muscle mass measured by BIA <7.0 kg/m2 for males and <5.7 kg/m2 for females (61), there is no diagnostic criterion for low muscle mass determined by BIA in EWGSOP2. This may be due to the heterogeneity of low muscle mass cut-off values among different ethnicities. Therefore, the cut-off values for low muscle mass range from 7.4 kg/m2−9.31 kg/m2 for males and from 5.14 kg/m2−7.4 kg/m2 for females, as shown in Table IV.

Table IV. Summary of research on BIA.

Table IV.

Summary of research on BIA.

First author/s, year	Population	BIA instrument	Criteria for cut-off point	Cut-off for low SMI (kg/m2)	(Refs.)
Pineda-Zuluaga et al, 2023	237 people, older than 60 years, Colombia	Hydra 4200 Xitron Technologies	−2 SD of the mean value of Colombia older adults	♂8.0; ♀6.1	(91)
Bulut et al, 2020	1,150 participants, >60 years old, Turkey	Tanita MC-780U	−2 SD of Turkish young adults (18 ~40 years old)	♂8.33; ♀5.7	(92)
Björkman et al, 2019	428 healthy people, >75 years, Finland	ImpediMed SFB7	Age-specific median values	♂9.31; ♀6.9	(93)
Han et al, 2016	878 healthy volunteers, >65 years, China	InBody 720	−2 SD of Chinese young adults (20~40 years old)	♂7.40; ♀5.14	(94)
Bahat et al, 2016	301 participants, Turkey	Tanita BC 532	−2 SD of Turkish young adults (18–39 years old)	♂9.2; ♀7.4	(95)

[i] BIA, bioimpedance analysis; SMI, skeletal muscle index.

The use of different evaluation instruments results in significant differences in cut-off values because different formulas are used to measure muscle mass. In the future, more studies should focus on establishing a unified and standardized instrument to explore the cut-off values for low muscle mass in different ethnicities, for the purpose of improving the sensitivity and specificity of sarcopenia screening. In general, BIA is a convenient and simple tool for measuring muscle mass and can be used in muscle mass screening for sarcopenia. However, it should be noted that muscle mass measurements by BIA are susceptible to the hydration status of patients, leading to inaccurate muscle mass values. Therefore, BIA is not recommended for patients with edema.

Discussion

Sarcopenia, a syndrome characterized by progressive and generalized loss of skeletal muscle mass and function, has gained recognition as a critical determinant of health in older adults (62). Accurate assessment of muscle mass is crucial for the diagnosis, monitoring and management of sarcopenia, markedly influencing clinical decision-making and patient outcomes (63). Anthropometric measurements such as CC, mid-upper arm circumference and the Yubi-wakka test, offer non-invasive, rapid and cost-effective approaches for sarcopenia screening (15). These methods are particularly valuable in both in community and hospital settings, enabling widespread screening initiatives (61). However, while the Yubi-wakka test shows good applicability in Asian populations, further validation in diverse ethnic groups is needed to ensure its global applicability (64). BIA is a widely used tool for assessing body composition, including muscle mass, owing to its ease of use and non-invasive nature. However, variability in BIA devices and methodologies can affect the accuracy and reliability of measurements, highlighting the need for standardization in sarcopenia diagnosis (65,66). Cut-off values for BIA in sarcopenia screening exhibit variability, with suggested thresholds being <7.0 kg/m2 for men and <5.5 or 5.7 kg/m2 for women (61). The EWGSOP recommends DXA for muscle mass assessment (39), due to its precision and ability to evaluate regional lean mass. However, its high cost and limited availability may restrict its use in routine clinical practice (67). The cut-off values for DXA in sarcopenia diagnosis are <7.0 kg/m2 for men and <5.4 kg/m2 for women. However, these thresholds may not be universally applicable across diverse populations (68). Imaging techniques such as CT and MRI provide detailed visualization of muscle mass and quality, making them valuable tools in sarcopenia research and clinical practice (31). The use of skeletal muscle mass measured at the L3 level serves as a common reference standard. However, the lack of standardized cut-off values and variability in the selection of vertebral levels and muscles for assessment pose significant challenges (69). Future research should prioritize the establishment of standardized criteria to enable more consistent diagnosis and monitoring of sarcopenia (70–72). US is emerging as a promising tool for sarcopenia assessment, offering a non-invasive, portable and repeatable method to evaluate muscle mass and quality (25). Its potential for real-time imaging and the absence of radiation exposure represent significant advantages. However, US results are operator-dependent and further research is required to establish its reliability and validity in sarcopenia assessment (55). Despite the variety of available methods, several challenges persist, such as the lack of standardized cut-off values across methodologies, the reliance on equipment that may not be universally accessible and the dependence on techniques requiring specialized training (63). The comparative merits and drawbacks of these measurement approaches are detailed in Table V. Additionally, the heterogeneity in sarcopenia presentation across diverse populations underscores the need for more inclusive research to ensure diagnostic accuracy (73). Given the limitations of individual methods, a combined approach may offer a more comprehensive assessment of sarcopenia. Integrating anthropometric measures with BIA or imaging techniques can yield a more accurate representation of muscle mass and function (58,74). Future research should explore the integration of these methods to improve diagnostic accuracy and enhance clinical applicability. The field of sarcopenia assessment is rapidly evolving, necessitating innovative approaches that balance accuracy with practicality for widespread implementation. The development of emerging technologies, such as advanced imaging software and machine learning algorithms, holds promise for delivering more precise and accessible methods for sarcopenia diagnosis (75). Furthermore, incorporation of biomarkers and genetic factors into the assessment framework could enable a more comprehensive understanding of sarcopenia (76).

Table V. Comparative analysis of body composition assessment modalities for sarcopenia evaluation.

Table V.

Comparative analysis of body composition assessment modalities for sarcopenia evaluation.

Methods	Strengths	Limitations
CT	• Quantitative gold standard	• Radiation burden
	• Widely available	• Threshold variability
	• Validated prognostic value	• Cost prohibitive for serial monitoring
MRI	• Superior soft tissue resolution	• Limited availability
	• Multi-parametric tissue characterization	• Lengthy acquisition
	• No ionizing radiation	• Motion artifacts
DXA	• Established reference ranges	• Hydration status confounding
	• Low radiation dose	• Regional variability
	• Rapid acquisition	• Limited quality assessment
	• Widely available
US	• Point-of-care application	• Operator expertise required
	• Dynamic muscle evaluation	• Limited reproducibility
	• Cost-effective	• Depth constraints
Anthropometry	• Universally accessible	• Insensitive to early changes
	• Minimal training required	• Body habitus confounding
	• Low-cost screening	• Qualitative only

[i] CT, Computed tomography; MRI, magnetic resonance imaging; DXA, Dual energy X-ray absorptiometry; US, ultrasound.

Sarcopenia is a prevalent condition among cancer patients, with significant implications for clinical outcomes. Current evidence establishes CT as the most widely adopted and clinically validated modality for body composition assessment in this population. The systematic review by McGovern et al (77) highlights that low SMI and skeletal muscle density, as assessed by CT, are prevalent across malignancies, independent of disease stage. However, the review underscores the lack of standardized thresholds for defining sarcopenia in oncology, with studies employing heterogeneous cut-offs. By contrast, Ubachs et al (78) provide compelling evidence for the prognostic value of CT-based assessments, demonstrating significant associations between both SMI [P=0.02; hazard ratio (HR): 1.17; 95% CI: 1.03–1.33] and skeletal muscle radiation attenuation (P<0.001; HR: 1.14; 95% CI: 1.08–1.20) with overall survival. The study highlights the particular clinical utility of CT in ovarian cancer, where ascites-related weight masking renders anthropometric measurements unreliable for nutritional assessment. The applicability of sarcopenia assessment varies markedly across cancer types, with methodology selection often dictated by anatomical considerations. Notably, studies in head and neck cancers predominantly employ cervical skeletal muscle index (C3 SMI) measurements, whereas investigations of gastrointestinal malignancies typically utilize lumbar skeletal muscle index (L3 SMI), reflecting site-specific clinical relevance (8). Other tools such as DXA (limited by hydration status), MRI (costly) and US (operator-dependent) are less robust for cancer-specific prognostication. Anthropometrics (such as CC) are accessible but lack precision. A meta-analysis by Zhang et al (8) systematically compared prognostic capabilities across skeletal muscle quantification methods, revealing that while L3 SMI remains the preferred modality for cross-cancer applications due to its standardized implementation, C3 SMI emerges as particularly predictive of mortality outcomes in head and neck malignancies; a finding that aligns with the anatomical and pathophysiological characteristics of these tumors. However, C3 SMI limited application in non-head/neck cancers restricts broader generalizability. Future research should prioritize tumor-specific diagnostic thresholds and multimodal assessment frameworks to optimize SMI assessment in cancer patients.

Normative values and cut-off criteria for muscle mass exhibit variations across ethnicities, sexes and age groups. However, a number of countries, including China, currently lack clinically validated cut-off standards and population-specific reference values derived from rigorous methodologies. To address this gap, future research is needed to determine benchmarks across diverse populations using advanced technologies, large-scale studies and high-quality methodologies. Future research should define clinically supported indices, such as FFM index in different ethnic groups, to determine sex- and age-specific normal ranges and clinically supported indices for diagnosing reduced muscle mass.

The present review presented a systematic evaluation framework that innovatively combined both conventional and emerging assessment modalities, thereby offering distinct methodological advantages compared with previous works by Muraki (methodological analysis) (79) and Li et al (technical imaging review) (80). The present review broadened the assessment paradigm by incorporating low-cost clinical tools including anthropometric measurements (such as CC) and validated self-assessment methods (such as the Yubi-wakka test), implemented through standardized diagnostic criteria (AWGS 2019) to enhance clinical utility across diverse settings without compromising diagnostic accuracy. Furthermore, the present review assessed multi-modal strategies, such as combining BIA with anthropometry, to improve accuracy while addressing limitations such as hydration effects or positioning errors, often overlooked in prior studies, with particular emphasis on population-specific validation for Asian cohorts to address diagnostic heterogeneity and technical rigor. Notably, the present review bridged research and practice by advocating harmonized protocols that balance gold-standard imaging (such as L3-CT) with scalable tools (such as US and CC), while also exploring emerging technologies such as machine learning for muscle segmentation. By comprehensively integrating multiple assessment approaches, our study extends the current evaluative paradigm to improve clinical utility.

Conclusion

While current methods provide valuable tools for both clinical practice and research, there remains a critical need for further standardization, validation and innovation. Future research should focus on the development and validation of assessment methods that are accessible, reliable and applicable across diverse populations, improving the care and outcomes for individuals affected by sarcopenia.

Acknowledgements

Not applicable.

Funding

The present study was supported by the Natural Science Foundation of Hunan Province (grant no. 2023JJ40907), the Natural Science Foundation of Changsha (grant no. kq2208355) and the Hunan Cancer Hospital Climb Plan (grant no. IIT2021005).

Availability of data and materials

Not applicable.

Authors' contributions

JH and CT conceived the study and contributed to the critical revision of the manuscript. WW and ML designed the study, collected data, prepared tables, drafted the original draft and conducted the review and editing. QZ contributed to manuscript drafting, prepared the tables, and reviewed the manuscript. Data authentication is not applicable. All authors read and approved the final manuscript.

Ethics approval and consent to participate

Not applicable.

Patient consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

References