Table 1.

Commonly used methods for assessing sarcopenia

Methods	How to	Units	Cut-offs	Pro	Cons
HGS	Measured using a hand dynamometer. The highest values for both right and left handgrip strength from two measurements were averaged, and then used for analysis	kg	M: < 27 kg W: < 16 kg M: < 30 kg W: < 15 kg	Validated cut-off; Simple and inexpensive	Not representative of overall sarcopenia
PMI	Total bilateral psoas muscle area at the middle of the third lumbar vertebra (L3) level (cm2), shown by CT, and height (m)	cm2/m2	M < 5.37 cm2/m2, W: < 3.4 cm2/m2 M: < 6.36 cm2/m2 W: < 3.92 cm2/m2	Simple and commonly used	Not representative of overall sarcopenia
TPV	Total psoas volume of the right psoas muscle was calculated semi‐automatically, by manual outlining of the boarders of the muscle, shown by CT, starting at the level of the last thoracic or first lumbar vertebra continuing until the psoas muscle becomes indistinguishable from the iliopsoas muscle	cm3	M: < 194.9 cm W: < 99.2 cm	Easy to calculate	Not representative of overall sarcopenia
PMTH	Psoas mass thickness, measured on CT at the level of the umbilicus, or at L3 or L4 was normalized by division by height	mm/m	16.8 mm/m at umbilicus level 14 mm/m al L4 level	Easy to calculate	Different level evaluated (L3, L4, umbilicus) Not representative of overall sarcopenia
TPMT	TPMT-L3: defined as the transversal diameter of the right psoas muscle perpendicular to the largest axial psoas muscle diameter at the L3 endplate, measured on CT. The results were normalized to body height TPMT‐umbilical: defined as the transversal diameter of the right psoas muscle perpendicular to the largest axial psoas muscle diameter at the level of the umbilicus. Results were normalized to body height	mm/m	M: < 10.7 mm/m W: < 7.8 mm/m	Easy to calculate	Different level evaluated The level of umbilicus could be influenced from ascites Not representative of overall sarcopenia
PSMI	Bilateral, total paraspinal muscle area (psoas major and minor muscles, quadratus lumborum muscles, transvers spinal muscles and erector spinae muscles) at the L3 endplate, measured on CT. The results were normalized by height	cm2/m2	M: < 26.3 cm2/m2 W: < 20.8 cm2/m2	CT images of a specific lumbar vertebral landmark (L3) correlated significantly with whole-body muscle	Not representative of overall sarcopenia
SMA	Assessed as the mean density (HU) of the entire measured cross-sectional muscle area at L3, measured on CT	HU	–	Reflect both to micro- and macroscopic changes in muscle architecture and composition	There is no universal consensus on this method for routine clinical practice
SMI	Skeletal muscles at the L3 or L4 level included the erector spinae, transverse abdominis, psoas, quadratus lumborum, internal and external oblique abdominal muscle and the rectus abdominis muscle, measured on CT, normalized for patient height	cm2/m2	L3 level: M: < 36.2 cm2/m2 W: ≤ 29.6 cm2/m2 M: < 52.4 cm2/m2 W: < 38.5 cm2/m2 W: < 41 cm2/m2 M: < 53 cm2/m2 With BMI > 25 and < 43 cm2/m2 with BMI > 25 L4 level:  < 52.4 cm2/m2	Most used CT based technique Precise measures of body composition	Different cut-offs
SMI by BIA	Appendicular SMM/height squared by BIA	kg/m2	M: < 7.0 kg/m2 W: < 5.5 kg/m2	BIA equipment is affordable, widely available and portable	BIA measurements can also be influenced by hydration status
MAMC	MAMC (cm) = MAC—(0.314 × TSF [mm])	cm	–	Easy to calculate; Simple and inexpensive	Not representative of overall sarcopenia
TSF	Measured by one experienced observer with caliper at the middle point between the acromion and the olecranon of the non-dominant arm	cm	–	Bedside technique Simple and inexpensive	Not representative of overall sarcopenia
LBM	0.306x[skeletal muscle at L3 using CT (cm2)] + 6.06	kg	–	CT images of a specific lumbar vertebral landmark (L3) correlated significantly with whole-body muscle	Not representative of overall sarcopenia
US- PTHR	Mean of psoas diameter divided, measured on US, by patient’s height	mm/m	–	US-based technique Assess both muscle quantity and quality	No valid cut-off
US-PMI	Psoas radius square, measured on US, divided by patient’s height square	cm2/m2	–	US-based technique Assess both muscle quantity and quality	No valid cut-off

BIA Bioelectrical impedance analysis, HGS handgrip strength, MAC Midarm circumference, MAMC midarm muscle circumference, PSMI Paraspinal muscle index, PMI psoas muscle index, SMA skeletal muscle attenuation, SMI skeletal muscle index, SMI skeletal muscle index, SMM skeletal muscle mass, TPV Total psoas volume, LBM Total lean body mass, TSF triceps skinfold thickness, TPMT Transversal psoas muscle thickness, PMTH psoas muscle thickness by height, US- PTHR Ultrasound Psoas to height ratio, US-PMI Ultrasound Psoas muscle index