Dittmar M, Reber H
Department of Biology, Institute of Anthropology, Gutenberg University, 55099 Mainz, Germany.
Am J Physiol Endocrinol Metab. 2001 Nov;281(5):E1005-14. doi: 10.1152/ajpendo.2001.281.5.E1005.
The objectives of this study were to assess for elderly Germans the validity of existing equations for predicting body cell mass (BCM) and to develop from single- and multifrequency bioimpedance (SFBIA, MFBIA) models new prediction equations. In a data-splitting approach, validation and cross-validation were performed in 160 healthy elderly (60- to 90-yr) subjects. BCM was determined using a tetrapolar bioimpedance analyzer (800 microA; 4 fixed frequencies: 1, 5, 50, and 100 kHz; electrodes placed to hand, wrist, ankle, and foot) and whole body (40)K counting as a reference method. New prediction equations were derived by multiple stepwise regression analysis. The Bland-Altman procedure was used for methods comparison. Relative to whole body counting, the manufacturer's equation overestimated BCM by 9% in men (P < 0.0001, paired t-test) and 4% in women (P = 0.002). Compared with the manufacturer's equation, the newly derived equations (r = 0.92, RMSE = 6-9%) improved accuracy (pure error = 13 vs. 7-8%) and reduced bias and limits of agreement. SFBIA and MFBIA equations did not differ in precision or accuracy. We conclude that the newly derived equations improved BCM estimates in the elderly compared with existing equations. There was no advantage of MFBIA over SFBIA equations.
本研究的目的是评估现有预测老年德国人体细胞质量（BCM）方程的有效性，并从单频和多频生物电阻抗（SFBIA、MFBIA）模型开发新的预测方程。采用数据分割方法，对160名健康老年人（60至90岁）进行了验证和交叉验证。使用四极生物电阻抗分析仪（800微安；4个固定频率：1、5、50和100千赫；电极置于手部、腕部、踝部和足部）测定BCM，并以全身（40）K计数作为参考方法。通过多元逐步回归分析得出新的预测方程。采用Bland-Altman方法进行方法比较。相对于全身计数，制造商的方程在男性中高估BCM 9%（P<0.0001，配对t检验），在女性中高估4%（P = 0.002）。与制造商的方程相比，新推导的方程（r = 0.92，RMSE = 6 - 9%）提高了准确性（纯误差 = 13对7 - 8%），并减少了偏差和一致性界限。SFBIA和MFBIA方程在精度或准确性方面没有差异。我们得出结论，与现有方程相比，新推导的方程改善了对老年人BCM的估计。MFBIA方程相对于SFBIA方程没有优势。
