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Kidney International, 2000 Jul;58(1):408-16.
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Comparing different methods of assessing body composition
in end-stage renal
failure.
B. A. Cooper, A. Aslani, M. Ryan, F. Y. Zhu, L. S. Ibels, B. J. Allen, C.
A. Pollock.
Department of Renal Medicine, Royal North Shore Hospital, University of
Sydney, New South Wales, Australia.
Abstract; Background: Accurate measurement of nutritional status in patients
with end-stage renal disease is important because of its clear association
with prognosis. Total body water (TBW) has additionally been recently
recognized as an independent prognostic value because of its relationship
with hypertension and cardiac morbidity. The current study was designed to
assess the utility of surrogate markers of nutritional state and TBW in
patients with end-stage renal disease.
Methods: Fifty-four patients with renal disease were studied. TBW obtained
using the deuterium dilution technique was compared with estimates derived
from anthropometric measures of TBW, including 58% body weight, Watson
equations, and bioelectrical impedance analysis (BIA). Anthropometrically
derived fat-free mass (FFM) was compared with BIA-derived estimates. Total
body nitrogen (TBN) measurements were correlated with TBW estimates and
BIA-derived resistance.
Results: TBW was significantly underestimated by the Watson equation (mean
difference, -1.751 L, P = 0.01) and the 58% body weight approximation
significantly overestimated it (mean difference, 1.792 L, P = 0.04). The
Kushner BIA estimation of TBW did not significantly differ from that of the
gold standard determined from D2O dilution (mean difference, -1.221 L, P =
0.12) and was also the method that showed the best agreement with the D2O
estimate. However, the limits of agreement were large. Accurate prediction
equations for FFM (FFM = -21.768 + 0.001 x ht^2 + 6630.669 x 1/R + 0.312 x
wt, R^2 = 0.95) and TBN (TBN = -668.324 - 3.963 x age + 10.133 x wt + 0. 045
x ht^2 + 32141.457 x 1/R, R^2 = 0.91) were derived from BIA obtained
resistance.
Conclusions: The estimation of TBW varies significantly depending on the method
of calculation. BIA is the most accurate surrogate marker for the measurement
of both TBW and other parameters of body composition. |
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