Total body water and percentage fat mass measurements using bioelectrical impedance analysis and anthropometry in spinal cord-injured patients

Background and aims: Spinal cord injured patients may be adversely affected by disturbances of nutritional status, particularly malnutrition and fat m ass overload. Malnutrition increases the risk for development of pressure s ores, and fat mass excess increases the cardiovascular and respiratory risk s of these patients, as well as predisposing to the development of diabetes mellitus, pressures sores and bony fractures. Body impedance analysis and anthopometry are easy bedside methods for body composition assessment. The aims of the study were to validate, in 20 spinal cord injured patients, bod y impedance analysis as a means to estimate total body water, and to valida te a skinfold measurement of percentage fat independent of hydration of fat -free mass in the same population. Methods: Total body water was measured by O-18 dilution as a reference meth od. Impedance and anthropometric measurements (four different skinfolds) we re obtained. The results of total body water given by impedance analysis an d calculated with three formulas were compared to the reference method. The fat mass percentage obtained with each of the skinfolds using the 3-compar tment Siri's formula was compared to a reference value using the sum of the skinfolds. Results and conclusion: The formula using 100 kHz resistance, height, weigh t and gender overestimated total body water by only 0.76 +/- 1.85 L, with a n acceptable concordance with labeled water results. The formula with 50 kH z resistance was less accurate and concordant. Each skinfold may be used fo r assessing percentage fat mass. Based on these findings, we feel that the triceps skinfold, whose the variability is the lowest compared to the refer ence values, can be used alone in clinical practice. (C) 2000 Harcourt Publ ishers Ltd.