MULTIPLE LABORATORY COMPARISON OF THE DOUBLY LABELED WATER TECHNIQUE

A double-blind study was conducted to determine between-laboratory var iability in the doubly labeled water method for measurement of total e nergy expenditure in humans, and to compare the accuracy and precision of three widely-used procedures for calculating rates of carbon dioxi de production from the original isotope data, Eighteen laboratories fr om five countries participated in the study, All laboratories were pro vided with five water standards containing varying amounts of H-2 and O-18, and in addition 11 laboratories were provided with urine and dos e specimens from one (six laboratories) or two (five laboratories) hea lthy elderly subjects of normal height and weight undergoing a calorim etric validation of the doubly labeled water method, The data from the five water standards were analyzed to predict between-laboratory vari ability in the doubly labeled water technique in all laboratories, In addition, data from the subjects were analyzed using the ''slope-inter cept'', ''2-point'' and ''modified'' methods of calculation. The resul ts confirm that the doubly labeled water method can be an accurate tec hnique for the measurement of energy expenditure in adult human subjec ts in some laboratories. However, there was substantial between-labora tory variability in the results and some laboratories returned physiol ogically impossible results, There was no significant effect of calcul ation procedure on the accuracy of the technique in this limited compa rison, although the slope-intercept procedure appeared to be more susc eptible to analytical error than the other procedures. The isotope sta ndards analyzed by participants in this study will be made available t o other investigators on request.