Table 2.

Advantages and limitations of methods used for the assessment of fat free mass and its compartments, muscle strength, and physical performance in patients with CKD

Methods	Method	Assessed compartments	Advantages	Limitations
Fat free massa
Anthropometry	MAMC Calf circumference APMT	SMM	Simple Can be used at the bedside Non-invasive Cheap	Low sensibility Difficulties caused by edema Need for high skilled anthropometrics
Bioelectrical impedance	BIA BIS	FFM TBM ECW	Can be used at the bedside Non-invasive Simple Cheap Provides information regarding nutritional and hydration status	Not a direct measure of lean mass Can be influenced by numerous factors (hydration status, body temperature, nutrition) Available equations that estimate SMM developed in community living elderly people Amputations and pacemakers preclude its use
Physical examination	Visual signs of muscle depletion in specific sites (temple, clavicle, shoulder, scapula/ribs, quadriceps, knee, calf, interosseous)	SMM estimation	Simple Requires no equipment Provides information regarding nutritional status Can be used at bed side	It is not an objective measurement, and therefore, not precise Not sensitive to small changes Requires detailed training
Imaging techniques	CT MRI	SMM	Highly accurate for assessing cross-sectional area and volume CT allows assessment of muscle density which provides information regarding muscle quality Not influenced by hydration status Allows whole body or regional evaluation	Uses ionized radiation (CT) Non-applicable at bedside Very expensive Need for specialized staff Variation between different machines Implanted metal precludes its use (MRI)
	DXA	LBM  FFM: LBM + bone  ALBM: LBM arms and legs	High precision Total body and regional evaluation Available in many hospitals	Low dose of ionized radiation Non-applicable at bedside Need for specialized staff High fixed cost (low variable costs) Do not differentiate extra-cellular from intra-cellular water
	Ultrasound	SMM	Can be used at the bedside Non-invasive Simple Cheap Reliable and repeatable Echogenicity allows assessment of muscle quality Assessment of cross-sectional area and thickness	Limited data on CKD patients No available cutoffs
Muscle strength
Grip strengthb	Handgrip dynamometer	Strength from upper limbs	Simple Portable Cheap Can be easily acquired for use in dialysis clinics, outpatient clinics and hospitals Does not require contribution from the examiner	May not represent strength in the lower limbs May not be suitable for patients with arthritis
Chair stand test	Five chair rise tests	Strength from lower and upper limbs	Simple Does not require equipment Can be easily performed in dialysis clinics, outpatient clinics and hospitals	Requires patient’s collaboration
Physical performance
Gait speed	Gait speed	NA	Easy to perform Suitable for clinical practice and research Does not requires equipment	Requires a space with a flat corridor
Short physical performance battery (SPPB)	Combination of three scores from tests: balance, gait speed and chair standc	NA	Easy to perform Does not require equipment	Requires the patient’s collaboration Requires a space with a flat corridor
Timed-up-and-go test (TUG)		NA	Easy to perform Does not require equipment	Cutoff points are not extensively validated as compared with gait speed and SPPB Requires a space with a flat corridor
400-m walk or long-distance corridor walk	TUG 400 m walk	NA	Easy to perform Does not require equipment	Requires a space with a flat corridor

ALBM Appendicular lean body mass, APMT adductor police muscle thicknesses, BIA bioelectrical impedance analysis, BIS bioelectrical impedance spectroscopy, CKD chronic kidney disease, CT computerized tomography, DXA dual energy x ray absorptiometry, ECW extracellular water, FFM fat free mass, LBM lean body mass, MAMC mid-arm muscle circumference, MRI magnetic resonance imaging, TBW total body water, SMM skeletal muscle mass, NA non-applicable

^aIn order to minimize influence from fluid retention, special care is advised for dialysis patients when assessing fat free mass. For those on hemodialysis, it should be evaluated after the hemodialysis session, and for patients on peritoneal dialysis after the drainage of the dialysis fluid from the peritoneal cavity [166–168]

^bFor patients on hemodialysis, assessment should be preferably performed before the dialysis session when handgrip strength was shown to be higher than after the dialysis session [169]

^cEach test is scored in 0 to 4 and the maximum score is 12 [170]