PURPOSE: to verify the validity of two octapolar bio-impedance analyzers (InBody 720 and InBody 320; Biospace, Co., Ltd., Seoul, Korea) for estimating intracellular water (ICW), extracellular water (ECW), and total body water (TBW) in a heterogeneous sample of adults (n = 111; 53 males and 58 females) aged 18–82 years.
METHODS: Participants received standard pre-testing guidelines within 48 hours of their scheduled sessions, and gave written, informed consent prior to participating. Height and weight were measured to the nearest 0.1 cm and 0.01 kg, respectively, with the participants barefoot and dressed in swimsuits. ICW, ECW, and TBW from the InBody analyzers was compared with reference values obtained using the Xitron 4200 bio-impedance analyzer (Xitron Technologies, San Diego, CA), which has been validated against deuterium dilution in adults. All measurements were performed according to the manufacturer's instructions, and the average of two repeat measures was used in the data analysis.
RESULTS: ICW, ECW, and TBW values from both octapolar analyzers were highly correlated with the reference values in the total sample (r = .938 - .960; p < .001), men (r = .822- .947; p < .001), and women (r = .822- .877; p< .001). However, paired-samples t-tests revealed significant mean differences between the InBody and Xitron 4200 bio-impedance analyzers (Table 1).
CONCLUSION: Relative to the Hydra 4200, both InBody analyzers overestimated ICW and underestimated ECW in adults aged 18–82 years. TBW was significantly overestimated in the total sample and women (p ≤ .001), but not men.