Table 2.

South Asian definition of sarcopenia and diagnostic tools for sarcopenia.

Sarcopenia: 2 of 3 rule: any two of the following should be present: muscle strength, muscle function and muscle mass
Clinical (primary modality of diagnosis)
Muscle strength		Muscle Function		Muscle Mass
Hand grip [19] Lower limb muscle strength [82]		Walking speed Sit-to stand [87] Chair stand test [88] SPPB [19]		Anthropometry CC/MAC/Thigh circumference BMI: weight and height Waist circumference
Imaging [18,19]
1.DXA [80,81]: Fat mass, lean soft tissue mass, and bone mineral content (localized or whole body); appendicular lean mass adjusted for BMI or height
2.BIA [82]: skeletal muscle mass index or appendicular skeletal muscle index
3.CT, MRI: Muscle mass, muscle density and fatty infiltration; differentiate between lean mass, bone and fat [62]
4.USG-M: Muscle mass
Biochemistry (proposed biomarkers)
Common laboratory tests [19,[182], [183], [184], [185]] Can be done at community/PHC level	Biomarker/s		Level in sarcopenia		What do biomarker levels in sarcopenia indicate?
	Albumin [186]; total protein [186], hemoglobin, vitamin D [187]; uric acid; magnesium, calcium [186], uric acid [186], triglycerides [186]		▼		Inadequate intake/underproduction
	Testosterone [188]		▼		Decreased muscle growth as it is muscle growth promoter
	Estrogen [189]		▼		Loss of beneficial effect of estrogen on skeletal muscle proliferation; increased inflammatory stress damage
	Creatine [190]		▼		Reduced muscle turnover
	CPK		▲		Muscle damage and inflammation
	CRP, ESR [186,191]		▲		Muscle inflammation
Specialized laboratory tests [19,94,185] Not routinely done; many are of academic interest and yet to be clinically relevant	Leptin [192]		▲		Impaired physical function
					Also increased in obesity induced sarcopenia (sarcopenic obesity)
	Follistatin [193]; brain-derived neurotrophic factor; bone morphogenetic proteins; IGF-1 [194]; growth hormone [194];		▼		Decreased muscle growth as individually each is a muscle growth promoter
	DHEAS [195,196]
	Serum cortisol/DHEAS ratio [196]		▲		Decreased muscle mass and strength, especially in diabetes mellitus patient
	Oxidized low-density lipoprotein		▲		The decrease in pro-oxidants levels reduce muscle protective action
	Selenium		▼		Inadequate intake
	vitamin C and vitamin E		▼		The decrease in antioxidants levels reduce muscle protective action
	Advanced glycosylation end-products (AGEs) [197]		▲		Altered muscle hemostasis (promoting muscle wasting), increased inflammation
					Also increased in sarcopenia secondary to diabetes, cancer, inflammatory skeletal muscle diseases and myopathies
	Protein carbonyls [198]		▲		Oxidative damage to muscle proteins; reduced muscle strength
	Adiponectin [186,199]		▲		Increase muscle inflammation and muscle metabolism
	Myostatin [200,201]; Growth differentiation factor-15; Activins A and B;		▲		Decreased muscle growth as individually each is a muscle growth suppressor
	Tumor growth factor β
	N-terminal type III procollagene		▼		Decreased muscle remodeling
	Interleukin 6 [191,202],		▲		Muscle inflammation
	GM-CSF, interferon γ,
	P-selectin,
	Tumor necrosis factor α [202]; Interleukin 1 and 8;		▼		Muscle inflammation
	Butyryl-cholinesterase, myeloperoxidase, MCP-1, macrophage inflammatory protein 1-α, PDGF BB
	3-methylhistidine [203]		▲		Proteolysis of myofibrils
	Skeletal muscle-specific troponin T		▲		Contractile insufficiency
	CAF [204]		▲		Impairment or degeneration of neuromuscular junctions
	Complement protein C1q		▲		Physical inactivity
	Cystatin C [205,206]		▲		Decreased muscle mass
	Secreted protein acidic and rich in cysteine (SPARC) [207]		▲		Reduced myogenesis
	Osteonectin, P3NP [208], fatty acid-binding protein-3, irisin [209], CAF, and macrophage migration inhibitory factor [207]		▲		These markers are increased in sarcopenia secondary to COPD or CHF
					Various MOAs:
					Increased muscle inflammation,
					Reduced HGS
					Reduced appendicular lean mass/height [2]
	Pre-Albumin		▼		Nutrition

BIA, Bio-electrical impedance analysis; CAF, c-terminal agrin fragment-22; CC, calf circumference; CHF, congestive heart failure; COPD, chronic obstructive pulmonary disease; CPK, creatinine phosphokinase; CRP, C-reactive protein; CT, computed tomography, DHEAS, dehydroepiandrosterone sulfate; DXA, Dual-energy X-ray absorptiometry; ESR, erythrocyte sedimentation rate; GM-CSF, granulocyte-monocyte colony-stimulating factor; HGS, hand grip strength; IGF-1, insulin like growth factor-1; MCP-1, monocyte chemoattractant protein 1; MOA, mechanism of action; MRI, magnetic resonance imaging; P3NP, procollagen type-III amino-terminal pro-peptide; PHC, primary health care; PDGF, platelet-derived growth factor BB; SPPB, Short Physical Performance Battery; USG-M, skeletal muscle ultrasound; ▼, decrease; ▲, increase.