[Consistency between bioelectrical impedance analysis and dual-energy X-ray absorptiometry for body composition measurement in children aged 7-17 years].

Objective: To evaluate the consistency between bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DXA) in the measurement of body composition in children and adolescents aged 7-17 years. Methods: Fat-free mass (FFM) and fat mass (FM) were measured by both BIA and DXA in 1 431 children. The consistency between the methods was evaluated by intra-class correlation coefficients (ICCs) and Bland-Altman analysis. Logarithmic transformation of both measurements was performed before Bland-Altman analysis. Results: The ICCs for FFM were 0.986 and 0.974 and ICCs for FM were 0.854 and 0.926 in boys and girls respectively. In boys, the mean ratio of FFMs by BIA and DXA was 1.04, with limits of Agreement (LoA) of 0.95-1.14, and in girls, the mean ratio of FFMs by BIA and DXA was 1.02, with the LoA of 0.90-1.15. The LoA of FFM became narrower with age in both boys and girls. Both boys and girls had the wide LoAs for FM (0.40-1.27 and 0.48-1.48, respectively). Additionally, the LoA ranges for FFM and FM narrowed with the increase of BMI level in both boys and girls. Conclusion: For all children, BIA showed good consistency with DXA for FFM, whereas significant errors occurred in FM measurement. The consistency between BIA and DXA was better for obese children than for underweight or normal-weight children.目的： 评价生物电阻抗法（BIA）与双能X线吸收法（DXA）测量7~17岁儿童青少年体成分的一致性。 方法： 对1 431名儿童进行BIA和DXA检测。采用组内相关系数（ICC）和Bland-Altman分析评价方法间所测去脂体重和脂肪量的一致性。Bland-Altman分析在对数变换的数据中进行。 结果： 男、女生中BIA与DXA所测去脂体重的ICC分别为0.986和0.974，脂肪量的ICC则分别为0.854和0.926。男生中BIA与DXA的去脂体重比值均值及一致性界限（LoA）分别为1.04和0.95~1.14，女生中则为1.02和0.90~1.15。男、女生中去脂体重的LoA范围均随年龄增长而变窄。男、女生中两种方法的脂肪量比值LoA范围均较宽，分别为0.40~1.27和0.48~1.48。此外，男、女生中均可看到各成分的比值LoA范围随BMI等级增高而变窄。 结论： BIA所测去脂体重与DXA的一致性良好，但BIA测量脂肪量的误差较大。肥胖儿童的BIA与DXA一致性优于消瘦和正常体重儿童。.