Direct Segmental Multi-Frequency Bioelectrical Impedance Analysis Is Useful to Evaluate Sarcopenia

Abstract

To the Editor:We are grateful to Safer et al. (1) for commenting on themethodology used in our recent study (2), and for definingsarcopenia. The validity of segmental bioelectrical imped-anceanalysis(BIA)forassessingskeletalmusclemassandthe significance of low muscle function in the diagnosis ofsarcopenia are important issues.Safer et al. argued that segmental BIA might not beappropriate for measuring muscle mass, referring to twoprevious papers from Japan and Europe. The BIA systemused in these studies is different from that used in ourrecent study (2). We used multifrequency BIA with atetrapolar eight-point tactile electrode system (InBody 720;Biospace, Tokyo, Japan), a newly developed directsegmental multifrequency BIA (DSM-BIA) system. Unlikeconventional BIA equipment, whichoften takes only partialmeasurements and therefore relies upon formulas toestimate whole body composition, this technique employsthe assumption that the human body is composed of fiveinterconnecting cylinders and takes direct impedancemeasurements from the various body compartments. Ofthe BIA devices developed over the years, the DSM-BIAsystem has been thus shown to be superior in theestimation of body composition (3). Ling et al. recentlydemonstratedexcellentagreementbetweenDSM-BIAanddualenergyX-rayabsorptiometry(DEXA)fortheestimationof lean body mass in both sexes in a large general middle-aged population (n ¼ 484) (4).In our recent report, no significant correlations wereobserved between the skeletal muscle mass and Child-Pugh classification (p ¼ 0.278). To rule out the possibilitythat BIA overestimated muscle mass in patients withoverhydration, including massive ascites and edema,which are often found in patients with Child-Pugh C liverdisease, we further divided 74 Child-Pugh C patients intothree groups according to the degree of ascites fluidretention (no ascites; 24, mild to moderate ascites; 24,massive ascites; 26), and compared skeletal muscle massamong them. Consequently, skeletal muscle mass in themassive ascites group (92.2 12.2) was significantlylower than that in the no ascites group (102.9 15.5;p ¼ 0.0286; Figure 1). Therefore, the effect of over-hydration on overestimation of BIA might be, if any,minimum in using this device, andthe deterioration of liverfunction caused by liver cirrhosis accompanied thedecreaseinskeletalmusclemassinChild-PughCpatients.A recent report demonstrating that lean body mass washighly correlated with good method agreement usingDEXAasthereferencetestin104stableperitonealdialysispatients (r ¼ 0.95, p < 0.0001) strongly supports theaccuracy of DSM-BIA, even in overhydrated patients (5).DSM-BIA is superior to DEXA in its simplicity, portability,lower cost, and absence of radiation exposure. Takingthese findings into consideration, DSM-BIA can be viewedas the gold standard for assessing sarcopenia.Evaluation of muscle function, in addition to muscle mass,would indeed be important for diagnosing sarcopenia. Asfor muscle function in patients undergoing liver transplan-tation, we are now conducting a prospective study, asdescribed in our recent paper. The interim analysis showsthat skeletal muscle mass is strongly correlated with gripstrength (data not shown); therefore, misclassification ofsubjects in our recent report would be, if any, almostnegligible.T. Kaido* and S. UemotoDivision of Hepato-Biliary-Pancreatic and TransplantSurgery, Department of Surgery, Graduate School ofMedicine, Kyoto University, Kyoto, Japan*Corresponding author: Toshimi Kaido,kaido@kuhp.kyoto-u.ac.jp