Table 1.

Methods to measure skeletal muscle mass

Tool	Accuracy (SD in kgs)	Advantages	Disadvantages
Bioelectrical impedance (BIA)	9.3	Safe; inexpensive; portable; expedient; no radiation	Relies on population-specific regressions not patient centered; not available at most cancer centers; skeletal muscle quality not evaluated; limited by BMI>34k/m2 that may overestimate muscle mass
Ultrasound (US)	NA	Safe; portable; expedient; low-cost; accessible; reliable for adipose tissue	No standardization technique (anatomical site, position or compression); patient habitus/hydration limitations and muscle contraction/relaxation state; operator dependent; provides muscle qualitative rather than quantitative measurements; no studies on cancer patients
Dual X ray absorptiometry (DXA)	3	Low-cost; can add limb muscle to trunk evaluation; low-radiation; better precision and accuracy	Low radiation exposure; cannot discriminate adipose and lean tissue; two-dimensional; influenced by tissue thickness and hydration; skeletal muscle quality not evaluated
Computed Tomography (CT)	<1.2	Clinically routinely accessible; accurately discriminates quantitative and qualitative muscle-fat body composition; high precision and reproducible predicting total LBM, CV=0.13–1.6%	Radiation exposure; dependent on a ‘slice’ at L3 availability; cannot accommodate large individuals in the scanner; presumed strong correlation to MRI not evaluated
Magnetic Resonance Imaging (MRI)	<1	Gold Standard; safe; excellent image quality; L3 level correlates with whole body scan (r: 0.924)	Costly and time consuming; not routinely used; cannot accommodate large individuals in the scanner