The use of portable A-mode ultrasound in appendicular lean mass measurements among older adults: a comparison study with dual-energy X-ray absorptiometry and handgrip strength.

Background/objectives: Strength and muscle mass are key factors for the diagnosis of sarcopenia. The EWGSOP2 recommended using ultrasound (US) as a reliable device to measure muscle mass (MM), but A-mode US still needs to be validated for older adults. This study aimed to evaluate the association between measurements of muscle thickness (MT) by portable A-mode US and, muscle quantity by Dual-Energy X-ray absorptiometry (DXA) in older adults.

Methods: Cross-sectional study, with 115 participants included. Muscle mass was assessed by DXA and MT of the biceps, triceps, anterior thigh, and calf by A-mode US and handgrip strength by a dynamometer.

Results: The majority were women (n = 96; 83%), 69 ± 6 years. The MT sum (biceps, triceps, thigh, and calf) assessed by the US was not associated with the appendicular lean mass (ALM) assessed by DXA after controlling for sex and age (R² = 0.524; p = 0.139; effect size = 0.53). The MT sum biceps and triceps was still significantly associated with MM arms/2 even when controlling for sex and age (which were also significant) (R² = 0.551; p < 0.001; effect size = 0.56). The MT sum thigh and calf was not associated with MM legs/2 in adjusted models (R² = 0.499; p = 0.688; effect size = 0.51).

Conclusions: This finding shows that the portable A-mode US may not be an appropriate method for estimating MM in extremities (the sum of arms and legs), but can be appropriate for estimating only MM arms in healthy older adults.