Royall D, Greenberg G R, Allard J P, Baker J P, Harrison J E, Jeejeebhoy K N
Toronto General Hospital, Department of Medicine, University of Toronto, Canada.
Am J Clin Nutr. 1994 Feb;59(2):325-30. doi: 10.1093/ajcn/59.2.325.
Bioelectric impedance analysis (BIA) has been widely used for assessment of body composition in healthy subjects but has not been validated in malnourished patients. This study compared calculation of fat-free mass (FFM) by five methods to determine whether the currently used equations for total body water (TBW) as assessed by BIA were applicable to 19 malnourished patients with Crohn's disease. When compared with TBW assessed by H2(18)O dilution, BIA was higher by 5.9 +/- 1.1% (P < 0.005). A stepwise-multiple-regression equation was derived to validate BIA: TBW (kg) = 0.25 (ht2/resistance) + 0.29 (wt) + 3.63 (r = 0.97, SEE = 0.28). Comparison of the hydration of FFM (TBW by 18O dilution/FFM) between methods showed that total body potassium (TBK) gave a significantly higher value when compared with the reference method of body protein, mineral, and 18O analysis. Dual-energy x-ray absorptiometry (DXA) provided a value for TBW/FFM in close agreement with the reference method. We conclude that BIA overestimates TBW, and TBK underestimates FFM in malnourished patients. DXA provides an accurate measurement of body fat in malnutrition.
生物电阻抗分析（BIA）已被广泛用于评估健康受试者的身体成分，但尚未在营养不良患者中得到验证。本研究比较了五种方法计算的去脂体重（FFM），以确定目前通过BIA评估的全身水（TBW）方程是否适用于19例克罗恩病营养不良患者。与通过H2(18)O稀释法评估的TBW相比，BIA高出5.9±1.1%（P<0.005）。推导了一个逐步多元回归方程来验证BIA：TBW（kg）=0.25（身高2/电阻）+0.29（体重）+3.63（r=0.97，SEE=0.28）。方法间FFM水合作用（通过18O稀释法测得的TBW/FFM）的比较表明，与身体蛋白质、矿物质和18O分析的参考方法相比，全身钾（TBK）给出的值明显更高。双能X线吸收法（DXA）提供的TBW/FFM值与参考方法密切一致。我们得出结论，在营养不良患者中，BIA高估了TBW，而TBK低估了FFM。DXA可准确测量营养不良患者的体脂。
