Cole T J, Coward W A
Medical Research Council Dunn Nutrition Unit, Cambridge, United Kingdom.
Am J Physiol. 1992 Nov;263(5 Pt 1):E965-73. doi: 10.1152/ajpendo.1992.263.5.E965.
Two-point or multipoint, that is the question. Equations are developed to compare the precision and accuracy of energy expenditure, as estimated from doubly labeled water data, when analyzed by the multipoint and two-point methods. The equations convert the enrichments of deuterium and oxygen-18 into their ratio and product, quantities that are less covariant than the two isotopes themselves are. This is important not only for estimating the precision but also as a graphical aid, since the ratios of the enrichments model carbon dioxide production, whereas the enrichment products largely model water turnover. Using data on 12 human subjects from the United Kingdom and The Gambia as examples, the combined precision and accuracy of the multipoint method (CV 3.6%) was found to be appreciably better than the two-point method (CV 5.4%). The bias in the multipoint estimate of body pool size would need to be three times as large as was observed before it canceled out the better precision.
两点法还是多点法，这才是问题所在。本文推导了一些方程，用于比较在通过多点法和两点法分析时，根据双标记水数据估算的能量消耗的精度和准确性。这些方程将氘和氧 - 18的富集度转换为它们的比值和乘积，这些量的协变量比这两种同位素本身要少。这不仅对于估计精度很重要，而且作为一种图形辅助手段也很重要，因为富集度的比值模拟二氧化碳的产生，而富集度的乘积在很大程度上模拟水的周转率。以来自英国和冈比亚的12名人类受试者的数据为例，发现多点法的综合精度和准确性（变异系数3.6%）明显优于两点法（变异系数5.4%）。在身体池大小的多点估计中的偏差需要比观察到的大三倍，才能抵消其更好的精度。
