Validation of body composition assessment techniques in the dialysis population.

Assessment of body composition remains a goal for the routine assessment of nutritional status of patients on long-term dialysis. Methods generally available for estimation of body fat in healthy individuals are limited by practicality and availability for use in this patient population. Anthropometry, which is cost effective and easy to perform, is limited by the lack of appropriate reference standards for patients on dialysis and artifact caused by hydration status. Bioelectrical impedance affords new opportunities for non-invasive assessment of fluid volume, its distribution, and body cell mass; estimation of fat-free mass and body fat can be affected by hydration status. Dual x-ray absorptiometry permits estimation of bone status and fat mass because changes in hydration status are reflected in estimates of fat-free mass. Evaluation of validity of techniques for fluid status and body composition assessment requires the use of appropriate reference methods and proper statistical procedures to examine error, not only between groups, but by individual. Use of body composition assessment methods together with biochemical measurements will enhance the nutritional assessment of end-stage renal disease patients on long-term hemodialysis.