Comparison of multifrequency bioimpedance measured lean mass to that calculated from anthropomometric measurements in patients with chronic kidney disease.

Patients with chronic kidney disease (CKD) are at increased risk of sarcopenia. Previous studies have proposed equations to estimate muscle mass based on triceps skin-fold thickness and mid-upper arm circumference, with or without adjustment for hand grip strength (HGS). We wished to evaluate their usefulness compared to multifrequency segmental bioimpedance (MFBIA) measured appendicular lean mass (ALM). We audited 160 CKD patients attending outpatient clinics, 65.6% male, median age 73 (62-81.5) years. We calculated muscle mass using six proposed equations based on anthropometric measurements. These equations over estimated muscle mass compared to MFBIA with a mean bias ranging from 3.4 to 35.9 kg. Apart from one equation, there was a systematic bias, with bias increasing with increasing fat mass (ranging from r = 0.17, p = 0.044 to r = 0.65, p < 0.001). For CKD patients we found that most of the previously proposed equations based on anthropometric equations over-estimated muscle mass compared to MFBIA.