Estimates of body water, fat-free mass, and body fat in patients on peritoneal dialysis by anthropometric formulas.
BACKGROUND
Anthropometric formulas that are used to estimate body water in peritoneal dialysis patients can also be used to estimate fat-free mass and body fat. Evaluation of body composition by the anthropometric formulas rests on two assumptions: (1) fat contains no water, and (2) the water content of the fat-free mass is constant (72%).


METHODS
We compared estimates of body water, fat-free mass, and body fat by anthropometric formulas to estimates employing dilution of tracer substances to measure body water and standard methods to analyze body composition in studies performed on peritoneal dialysis patients. We also analyzed the potential errors of the estimates of body composition by the formulas.


RESULTS
Estimates of the average body composition provided by the anthropometric formulas agreed with estimates provided by the standard methods. However, these formulas have the potential of introducing large errors when estimating body composition in individuals differing from the average subject, either because the anthropometric formulas do not account for major determinants of body composition, such as physical exercise, nutrition, and catabolic illness, or because these formulas systematically overestimate body water in subjects who are obese or experiencing volume excess.


CONCLUSIONS
Anthropometric formulas currently in existence can provide only approximations of body composition and may be the sources of large errors in evaluating body composition in peritoneal dialysis patients. The potential errors include estimates of body water. These errors may alter the interpretation of urea kinetic studies in certain categories of peritoneal dialysis patients (e.g., obese subjects).
Tzamaloukas
Antonios H
AH
Medicine Service, New Mexico Veterans Affairs Health Care System and University of New Mexico School of Medicine, Albuquerque, New Mexico 87108, USA. Tzamaloukas.Antonios@Albuquerque.va.gov
Murata
Glen H
GH
Vanderjagt
Dorothy J
DJ
Glew
Robert H
RH
D000273:Adipose Tissue / Q000033:anatomy & histology*; D015992:Body Mass Index; D001834:Body Water; D006801:Humans; D007676:Kidney Failure, Chronic / Q000628:therapy*; D010530:Peritoneal Dialysis