Influence of delayed isotopic equilibration in urine on the accuracy of the 2H218O method in the elderly

• Published in: Journal of applied physiology (1985) 2002-03, Vol.92 (3), p.1036-1044
• Main Authors: Blanc, Stephane, Colligan, Amanda S, Trabulsi, Jillian, Harris, Tamara, Everhart, James E, Bauer, Doug, Schoeller, Dale A
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Metabolisms and neurohumoral controls; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Water and mineral metabolism. Osmoregulation. Acidobasic balance
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00743.2001

1  Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53706-1571; 2  National Institute on Aging and 3  National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892; and 4  Prevention Sciences Group, University of California, San Francisco, California 94143 Isotopic determination of total energy expenditure (TEE) by the doubly labeled water (DLW) method may be affected by urine retention in the elderly. The isotopic enrichments in urine and plasma sampled simultaneously 4 h post-DLW dose were compared in a subset of 281 subjects [139 women, 142 men, 75 ± 3 (SD) yr] of the 3,075 participants in the Health, Aging, and Body Composition study. Based on analytic precisions, a ±2% urine-plasma difference was set as the cut-off value. Ten percent of the population presented a difference lower than 2%, suggesting a delay in urine isotopic equilibration. This 13 ± 10% urine-plasma difference was not linked to analytic errors, illnesses, the sampling time, or the time and quantity of water intake, suggesting that urine retention may be the main factor. The consequences are an 18 ± 13 and 21   ± 16% overestimation of the total body water and the TEE, respectively. Unexpectedly, 21% of the population presented a urine-plasma difference higher than ±2% that resulted, however, in a nonsignificant TEE underestimation of 3 ± 5%. In conclusion, the delayed isotopic equilibration observed in urine reduces the accuracy of the DLW method in the elderly. It is recommended, when blood sampling is impossible, to adopt the intercept method with urine sampling 24 h postdose. aging; energy requirements; deuterium; oxygen-18