ACCURACY AND RELIABILITY OF TOTAL-BODY ELECTRICAL-CONDUCTIVITY (TOBEC) FOR DETERMINING BODY-COMPOSITION OF RATS IN EXPERIMENTAL STUDIES

Total body electrical conductivity (TOBEC) has been promoted as a noni nvasive method to estimate body composition in small mammals. Validati on of this method has primarily been under normative conditions and ha s generally been inadequate. This article reports on the reliability a nd accuracy of TOBEC methodology to assess gradual, physiologically in duced changes in body composition in rats under different experimental conditions. Reliability of the index of electrical conductivity (EM n umber) was assessed by analyzing components of variance. Accuracy was assessed by comparing EM number to actual lean body mass (LBM, from ca rcass analysis), across different experimental conditions, within a pa rticular experimental condition, and over time for a given set of anim als. Reliable measurements were obtained by strictly adhering to a sta ndard protocol. TOBEC was inaccurate across experimental conditions, w ithin experimental conditions, and within a single experimental condit ion during the course of an experiment. This inaccuracy apparently ste mmed from the lack of a direct relationship between EM number and LBM; EM number was more strongly correlated with body weight than with LBM . At the present time, TOBEC cannot be used in place of carcass analys is to accurately predict the body composition of rats during or follow ing the administration of a variety of experimental conditions.