Utility of Ultrasound as a Valid and Accurate Diagnostic Tool for Sarcopenia

Objectives Patients with chronic kidney disease (CKD) have aberrant changes in body composition, including low skeletal muscle mass, a feature of “sarcopenia.” The measurement of the (quadriceps) rectus femoris (RF) cross‐sectional area (CSA) is widely used as a marker of muscle size. Cutoff values are needed to help discriminate the condition of an individual's muscle (eg, presence of sarcopenia) quickly and accurately. This could help distinguish those at greater risk and aid in targeted treatment programs. Methods Transverse images of the RF were obtained by B‐mode 2‐dimensional ultrasound imaging. Sarcopenic levels of muscle mass were defined by established criteria (1, appendicular skeletal muscle mass [ASM]; 2, ASM/height 2 ; and 3, ASM/body mass index) based on the ASM and total muscle mass measured by a bioelectrical impedance analysis. The discriminative power of RF‐CSA was assessed by receiver operating characteristic curves, and optimal cutoffs were determined by the maximum Youden index (J). Results One hundred thirteen patients with CKD (mean age [SD], 62.0 [14.1] years; 48% male; estimated glomerular filtration rate, 38.0 [21.5] mL/min/1.73m 2 ) were included. The RF‐CSA was a moderate predictor of ASM ( R 2 = 0.426; P < .001) and total muscle mass ( R 2 = 0.438; P < .001). With a maximum J of 0.47, in male patients, an RF‐CSA cutoff of less than 8.9 cm 2 was deemed an appropriate cutoff for detecting sarcopenic muscle mass. In female patients, an RF‐CSA cutoff of less than 5.7 cm 2 was calculated on the basis of ASM/height 2 (J = 0.71). Conclusions Ultrasound may provide a low‐cost and simple means to diagnose sarcopenia in patients with CKD. This would allow for early management and timely intervention to help mitigate the effects in this group.