Williams Jane E, Wells Jonathan C K, Wilson Catherine M, Haroun Dalia, Lucas Alan, Fewtrell Mary S
MRC Childhood Nutrition Research Centre, Institute of Child Health, London, UK.
Am J Clin Nutr. 2006 May;83(5):1047-54. doi: 10.1093/ajcn/83.5.1047.
Dual-energy X-ray absorptiometry (DXA) is widely used to assess body composition in research and clinical practice. Several studies have evaluated its accuracy in healthy persons; however, little attention has been directed to the same issue in patients.
The objective was to compare the accuracy of the Lunar Prodigy DXA for body-composition analysis with that of the reference 4-component (4C) model in healthy subjects and in patients with 1 of 3 disease states.
A total of 215 subjects aged 5.0-21.3 y (n = 122 healthy nonobese subjects, n = 55 obese patients, n = 26 cystic fibrosis patients, and n = 12 patients with glycogen storage disease). Fat mass (FM), fat-free mass (FFM), and weight were measured by DXA and the 4C model.
The accuracy of DXA-measured body-composition outcomes differed significantly between groups. Factors independently predicting bias in weight, FM, FFM, and percentage body fat in multivariate models included age, sex, size, and disease state. Biases in FFM were not mirrored by equivalent opposite biases in FM because of confounding biases in weight.
The bias of DXA varies according to the sex, size, fatness, and disease state of the subjects, which indicates that DXA is unreliable for patient case-control studies and for longitudinal studies of persons who undergo significant changes in nutritional status between measurements. A single correction factor cannot adjust for inconsistent biases.
双能X线吸收法（DXA）在研究和临床实践中被广泛用于评估身体成分。多项研究评估了其在健康人群中的准确性；然而，在患者中针对同一问题的关注较少。
比较Lunar Prodigy DXA在健康受试者以及患有三种疾病状态之一的患者中进行身体成分分析的准确性与参考四成分（4C）模型的准确性。
总共215名年龄在5.0 - 21.3岁的受试者（n = 122名健康非肥胖受试者，n = 55名肥胖患者，n = 26名囊性纤维化患者，n = 12名糖原贮积病患者）。通过DXA和4C模型测量脂肪量（FM）、去脂体重（FFM）和体重。
DXA测量的身体成分结果的准确性在各组之间存在显著差异。在多变量模型中，独立预测体重、FM、FFM和体脂百分比偏差的因素包括年龄、性别、体型和疾病状态。由于体重的混杂偏差，FFM中的偏差并未在FM中反映出等效的相反偏差。
DXA的偏差因受试者的性别、体型、肥胖程度和疾病状态而异，这表明DXA对于患者病例对照研究以及对在测量期间营养状况发生显著变化的人群进行纵向研究而言是不可靠的。单一校正因子无法校正不一致的偏差。
