Lazzer Stefano, Bedogni Giorgio, Agosti Fiorenza, De Col Alessandra, Mornati Daniela, Sartorio Alessandro
Istituto Auxologico Italiano, IRCCS, Laboratorio Sperimentale Ricerche, Auxo-endocrinologiche, Verbania, Italia.
Br J Nutr. 2008 Oct;100(4):918-24. doi: 10.1017/S0007114508922558. Epub 2008 Feb 18.
The objectives of the present study were to compare body composition assessed by dual-energy X-ray absorptiometry (DXA), air displacement plethysmography (ADP) and bioelectrical impedance analysis (BIA) in severely obese Caucasian children and adolescents and to develop and validate new equations for predicting body composition from BIA using DXA as the reference method. Body composition was assessed in fifty-eight obese children and adolescents (BMI 34.4 (SD 4.9) kg/m(2)) aged 10-17 years by DXA, ADP and BIA. ADP body fat content was estimated from body density using equations devised by Siri (ADP(Siri)) and Lohman (ADP(Lohman)). In the whole sample, the Bland-Altman test showed that ADP(Siri) and ADP(Lohman) underestimated percentage fat mass (%FM) by 2.1 (SD 3.4) and by 3.8 (SD 3.3) percent units (P<0.001), respectively, compared to DXA. In addition, compared to DXA, BIA underestimated %FM by 5.8 (SD 4.6) percent units in the whole group (P<0.001). A new prediction equation (FFM (kg) = 0.87 x (stature(2)/body impedance) + 3.1) was developed on the pooled sample and cross-validated on an external group of sixty-one obese children and adolescents. The difference between predicted and measured FFM in the external group was -1.6 (SD 2.9) kg (P<0.001) and FFM was predicted accurately (error < 5%) in 75% of subjects. In conclusion, DXA, ADP and the BIA are not interchangeable for the assessment of %FM in severely obese children and adolescents. The new prediction equation offers an alternative approach to DXA for the estimation of body composition in severely obese children and adolescents.
本研究的目的是比较双能X线吸收法（DXA）、空气置换体积描记法（ADP）和生物电阻抗分析（BIA）在重度肥胖的白种儿童和青少年中对身体成分的评估，并开发和验证以DXA作为参考方法，通过BIA预测身体成分的新方程。采用DXA、ADP和BIA对58名10至17岁的肥胖儿童和青少年（BMI 34.4（标准差4.9）kg/m²）的身体成分进行评估。ADP体脂含量根据Siri（ADP(Siri)）和Lohman（ADP(Lohman)）设计的公式，由身体密度估算得出。在整个样本中，Bland-Altman检验显示，与DXA相比，ADP(Siri)和ADP(Lohman)分别低估脂肪量百分比（%FM）2.1（标准差3.4）和3.8（标准差3.3）个百分点（P<0.001）。此外，与DXA相比，BIA在整个组中低估%FM 5.8（标准差4.6）个百分点（P<0.001）。在合并样本上开发了一个新的预测方程（去脂体重（kg）=0.87×（身高²/身体阻抗）+3.1），并在另一组61名肥胖儿童和青少年中进行交叉验证。外部组中预测的去脂体重与测量值之间的差异为-1.6（标准差2.9）kg（P<0.001），75%的受试者去脂体重预测准确（误差<5%）。总之，在评估重度肥胖儿童和青少年的%FM时，DXA、ADP和BIA不可互换使用。新的预测方程为评估重度肥胖儿童和青少年的身体成分提供了一种替代DXA的方法。
