Abstract
Extract: The whole body counter has provided a fast and accurate method of determining the total body potassium (TBK) of an individual. The interpretation of a single determination does present difficulties because of individual differences in body composition. The normal range, expressed in milliequivalents per kilogram, is so wide that an individual can lose 33% of his TBK and the result be interpreted as normal. To overcome this problem the prediction of the normal TBK of an individual from functions of weight (W), height (H), and skinfold thickness has been investigated and the accuracy of prediction of TBK and log TBK by various functions of weight, height, and skinfold thickness compared. Eighty-seven children aged 1.5–27 months and of varying height and weight for age were studied. None had any abnormality which may have resulted in potassium depletion at the time of study. The best prediction of TBK (in milliequivalents or milliequivalents per kilogram) by functions of weight and or height f(W,H) had 95% tolerance limits of 100% ± 18.2%. Using a function of the log transformation of mean skinfold thickness including a f(W,H) narrowed the tolerance limits to ± 6%. The best prediction of the log TBK (in milliequivalents or milliequivalents per kilogram) by f(W,H) gave tolerance limits of ±3.3%–4.8%. The best prediction of the log TBK in milliequivalents was f(W,H) and log transformation of mean skinfold thickness which gave narrow 95% tolerance limits of 100 ± 1.3%.
Speculation: In nonedematous children a function of (W/H)1/4, W/H2, and log transformation of skinfold thickness is an accurate predictor of the log TBK in milliequivalents. The narrow 95% tolerance limits allow the detection of small deviations from normal. The measurement of skinfold thickness is inaccurate in edematous patients and the TBK has to be predicted from f(W,H) alone. The tolerance limits for the prediction of log TBK in milliequivalents by (W/H)1/4 and W/H2 are still narrow. The accurate prediction of the normal TBK of an individual by simple anthropologic measurements enhances the clinical value of TBK determinations. Relatively small deviations from normal can be detected in edematous and nonedematous children.
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Mann, M., Bowie, M. & Hansen, J. Total Body Potassium Estimations in Young Children: The Interpretation of Results. Pediatr Res 8, 879–884 (1974). https://doi.org/10.1203/00006450-197411000-00005
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DOI: https://doi.org/10.1203/00006450-197411000-00005