ANALYTIC REQUIREMENTS FOR THE DOUBLY LABELED WATER METHOD

The doubly labeled water method is the first method that accurately me asures total daily energy expenditure in free-living subjects over per iods of days to weeks, Validations have indicated that the method can be performed with a coefficient of variation of between 3% and 5%, Thi s precision, however, is dependent on the quality of the isotopic anal yses, A recent interlaboratory comparison has indicated that there is a wide variation in the accuracy and precision with which deuterium an d O-18 enrichments are measured, This reduces the accuracy and precisi on with which a laboratory will perform the doubly labeled water metho d and in some cases may limit the application of this technique, Herei n we review the analytical requirements for optimal use of the method and some of the potential sources of error in the stable isotope analy sis.