Sarcopenia and frailty: An in-depth analysis of the pathophysiology and effect on liver transplant candidates

Table 1 Assessment methods for sarcopenia

Method	Measurement	Description	Advantages	Disadvantages
HGS	Muscle strength (kg)	Uses a dynamometer to measure hand grip force, indicating overall muscle strength	Simple, non-invasive, and cost-effective; strong correlation with overall muscle function	Affected by motivation, hand injuries, and neurological conditions
Gait speed	Walking speed (meter/second)	Measures the time taken to walk a set distance (e.g., 4-6 meters), assessing mobility	Quick and easy to perform; predictive of disability and mortality	Influenced by joint pain, neurological conditions, and cardiovascular fitness
SPPB	Composite score (0-12)	Includes balance, gait speed, and chair stand tests to assess lower limb function	Comprehensive evaluation; predicts adverse outcomes	Requires trained personnel and space for testing
Chair stand test	Time to complete 5 sit-to-stand repetitions (second)	Evaluates lower limb strength by timing how long a person takes to rise from a chair without arm support	Functional test; easy to administer	Affected by arthritis, balance disorders, and pain
DXA	ALM in kg/m²	Measures muscle mass through low-dose X-ray imaging, considered a gold standard	Accurate, reliable, and widely used in research	Expensive; limited availability in clinical settings
BIA	SMI	Uses electrical currents to estimate body composition, including muscle mass	Portable, affordable, and non-invasive	Less accurate in patients with fluid imbalances
CT/MRI	Cross-sectional muscle area and density	Directly visualizes muscle tissue and fat infiltration in specific body regions	Highly precise and can assess muscle quality	Expensive; CT involves radiation exposure

HGS: Handgrip strength; SPPB: Short physical performance battery; DXA: Dual-energy X-ray absorptiometry; BIA: Bioelectrical impedance analysis; CT: Computed tomography; MRI: Magnetic resonance imaging; ALM: Appendicular lean mass; SMI: Skeletal muscle mass index.

Table 2 Assessment methods for frailty

Method	Measurement	Description	Advantages	Disadvantages
Fried frailty phenotype	Five criteria (weight loss, exhaustion, weakness, slow walking speed, low activity)	Categorizes frailty as robust, pre-frail, or frail based on physical function	Simple, widely used, and validated	Requires physical performance testing; does not assess cognitive or social frailty
FI (rockwood model)	Score based on accumulation of health deficits (0-1)	Considers comorbidities, functional impairments, and cognitive decline	Comprehensive assessment of overall health status	Time-consuming; requires detailed clinical data
CFS	9-point scale (1: Very fit, 9: Terminally ill)	Visual tool assessing frailty severity based on clinical judgment	Quick and easy to use in hospital settings	Subjective; relies on clinician expertise
GFI	15-item questionnaire covering physical, cognitive, and social frailty	Self-reported tool for community-dwelling older adults	Easy to administer; non-invasive	May not detect early frailty signs; self-reported bias
EFS	10 domains, including cognition, mood, function, and nutrition	Multidimensional tool covering multiple frailty aspects	Covers both physical and cognitive factors	Requires trained personnel to administer

FI: Frailty index; CFS: Clinical frailty scale; GFI: Groningen frailty indicator; EFS: Edmonton frail scale.

Table 3 Commonly used computed tomography-based cut-off values for sarcopenia diagnosis at the L3 vertebral level

Ref.	Study population	Cut-off for males (cm²/m²)	Cut-off for females (cm²/m²)	Key considerations
Carey et al[25], 2017	Patients with cirrhosis	< 50	< 39	Developed for pre-liver transplant evaluation; validated against DXA-derived ALMI
Prado et al[26], 2008	Oncology patients	< 52.4	< 38.5	Derived from cancer cohorts; used broadly in nutritional and body composition studies
Montano-Loza et al[27], 2014	Liver transplant candidates	< 50	< 39	Consistent with Carey et al[25]; widely cited in hepatology for transplant risk stratification
Martin et al[73], 2013	Cancer patients (BMI-adjusted)	< 43 (BMI < 25)/< 53 (BMI ≥ 25)	< 41	Incorporates BMI to adjust thresholds; primarily used in oncology

DXA: Dual-energy X-ray absorptiometry; ALMI: Appendicular lean mass index; BMI: Body mass index.