Utility of multi‐frequency bioelectrical impedance compared to deuterium dilution for assessment of total body water

Aim Multi‐frequency bioelectrical impedance analysis (MF‐BIA) may provide a quick, cost‐efficient method of total body water (TBW) assessment. We compared TBW estimates from the Biospace InBody 520, 720, and S10 MF‐BIA devices to TBW estimates from isotopic deuterium dilution (D2O). Methods TBW was measured in 25 men and 25 women, 18–49 years, 73.6 ± 15.4 kg on each of the three devices and from D2O analysis. Results All MF‐BIA devices significantly overestimated TBW compared to D2O TBW for men (4.7–5.4 kg, 10.8–12.4%; P < 0.01) and women (3.7–4.3 kg, 12.3–14.3%; P < 0.01). Regression analyses in men revealed R2 (0.86–0.90) and SEE (1.7–2.0 kg), and in women revealed R2 (0.82–0.86) and SEE (1.5–1.6 kg). Bland and Altman analyses revealed similar limits of agreement for men (3.5–3.9 kg) and women (3.4–3.7 kg). Conclusions The Biospace InBody devices significantly overestimate TBW in men and women. The consistent bias for men and the increasing bias with increasing TBW for women may indicate that these devices are suitable for group TBW estimates in men only.