Measuring Muscle Mass to Identify Sarcopenia Via Bioelectrical Impedance Analysis in Hemodialysis: Importance of Timing and Equipment Choice

Measurement of muscle mass is an integral part of sarcopenia diagnosis. Bioelectrical impedance analysis has been commonly used for muscle mass assessment in many clinical and research settings as it is non-invasive, practical, and portable. However, one of the major handicaps of this measurement technique is that the validity and precision of bioelectrical impedance analysis measurements can be affected by hydration status. In hemodialysis patients, the volume status fluctuates easily and continuously, which is most significant between the immediate pre -dialysis and post -dialysis periods. Thus, a significant difference in the results of bioelectrical impedance analysis measurement is obviously expected between that obtained before and after hemodialysis. In fact, many centers perform measurements before hemodialysis, since it is more convenient for both staff and patients. However, the confounding effect of excess water on correct bioelectrical impedance analysis estimations seems substantial. For this reason, it seems more appropriate to perform bioelectrical impedance analysis measurements in chronic hemodialysis patients when they are closer to their dry weight, i.e., after the dialysis rather than before it. Accordingly, we searched the literature to identify the ideal timing of bioelectrical impedance analysis measurements in patients undergoing hemodialysis. The literature data on this subject indicate that performing bioelectrical impedance analysis measurements in the period after 15 minutes and within 2 hours after hemodialysis session will aid in a better estimation of muscle mass in terms of reliability and reproducibility.