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 mass overload. Malnutrition increases the risk for development of pressure sores, and fat mass excess increases the cardiovascular and respiratory risks 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, body impedance analysis as a means to estimate total body water, and to validate 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 method. Impedance and anthropometric measurements (four different skinfolds) were obtained. The results of total body water given by impedance analysis and calculated with three formulas were compared to the reference method. The fat mass percentage obtained with each of the skinfolds using the 3-compartment 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, weight and gender overestimated total body water by only 0.76 +/- 1.85 L, with an acceptable concordance with labeled water results. The formula with 50 kHz resistance was less accurate and concordant. Each skinfold may be used for assessing percentage fat mass. Based on these findings, we feel that the triceps skinfold, whose the variability is the lowest compared to the reference values, can be used alone in clinical practice. (C) 2000 Harcourt Publishers Ltd.