Investigations
1st investigations to order
serum electrolytes
Test
Request for all patients to rule out medical conditions and identify secondary causes of sarcopenia.
Result
normal
blood glucose
Test
Request for all patients to rule out medical conditions and identify secondary causes of sarcopenia.
Result
normal
LFTs
Test
Request for all patients to rule out medical conditions and identify secondary causes of sarcopenia.
Result
normal
renal function tests
Test
Request for all patients to rule out medical conditions and identify secondary causes of sarcopenia.
Result
normal
thyroid function tests
Test
Request for all patients to rule out medical conditions and identify secondary causes of sarcopenia.
Result
normal
FBC
Test
Request for all patients to exclude medical conditions and identify secondary causes of sarcopenia.
Result
normal
serum vitamin D
Test
Request in all patients with sarcopenia to help inform decisions about supplementation in patients with vitamin D deficiency.
Result
normal
dual-energy x-ray absorptiometry (DXA)
Test
DXA is the imaging technique recommended by the International Conference on Frailty and Sarcopenia Research to determine the level of lean body mass when diagnosing sarcopenia, due to its higher accessibility and lower cost and radiation exposure compared with CT and MRI.[2]
However, DXA cannot account for fatty infiltration of muscle, which can lead to an overestimation of lean mass.
In practice, where it is not possible to measure muscle mass (or there will be delay in doing so), treatment for sarcopenia should be initiated based on low muscle strength alone.
Result
appendicular skeletal muscle <20 kg for men and <15 kg for women; appendicular skeletal mass index <7.0 kg/m² for men and <5.5 kg/m² for women
CT
Test
CT is one of the recommended tests for estimating muscle volume and quality in patients identified clinically as having probable sarcopenia.[1][2] CT delivers high radiation levels.
In practice, where it is not possible to measure muscle mass (or there will be delay in doing so), treatment for sarcopenia should be initiated based on low muscle strength alone.
Result
low muscle mass and muscle quality (intramuscular fat infiltration)
MRI
Test
MRI is one of the recommended tests for estimating muscle volume and quality in patients identified clinically as having probable sarcopenia.[1][2] MRI requires the absence of metallic implants or devices such as a pacemaker.
In practice, where it is not possible to measure muscle mass (or there will be delay in doing so), treatment for sarcopenia should be initiated based on low muscle strength alone.
Result
low muscle mass and muscle quality (intramuscular fat infiltration)
Investigations to consider
bioimpedance analysis (BIA)
Test
BIA measures the rate at which a painless low-voltage electrical current travels through the body. It is based on the principle that different tissues in the body allow the electrical current to travel at distinct speeds. Fat is more resistant than muscle or water, so the higher the resistance, the higher the body fat percentage. The equipment is widely available, portable, and affordable.[1] However, it is less accurate than DXA.[2]
Different machines used for BIA produce different results, which are not comparable. Also, different populations require different equations to calculate muscle mass. Using BIA in clinical practice can only be done accurately when validation of a particular machine/population combination is available.
Result
<7.0 kg/m² in men and <5.7 kg/m² in women
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