Accuracy of eight-polar bioelectrical impedance analysis for the assessment of total and appendicular body composition in peritoneal dialysis patients.

OBJECTIVE: To establish the accuracy of bioelectrical impedance analysis (BIA) for the assessment of total and appendicular body composition in peritoneal dialysis (PD) patients. DESIGN: Cross-sectional study. SETTING: University Nephrology Clinic. SUBJECTS: In all, 20 PD patients and 77 healthy controls matched for gender, age and body mass index. METHODS: Whole-body fat-free mass (FFM) and appendicular lean tissue mass (LTM) were measured by dual-energy X-ray absorptiometry. Resistance (R) of arms, trunk and legs was measured by eight-polar BIA at frequencies of 5, 50, 250 and 500 kHz. Whole-body resistance was calculated as the sum of R of arms, trunk and legs. The resistance index (RI) was calculated as the ratio between squared height and whole-body or segmental R. RESULTS: RI at 500 kHz was the best predictor of FFM, LTM(arm) and LTM(leg) in both PD patients and controls. Equations developed on controls overestimated FFM and LTM(arm) and underestimated LTM(leg) when applied to PD patients. Specific equations were thus developed for PD patients. Using these equations, the percent root mean-squared errors of the estimate for PD patients vs controls were 5 vs 6% for FFM, 8 vs 8% for LTM(arm) and 7 vs 8% for LTM(leg). CONCLUSION: Eight-polar BIA offers accurate estimates of total and appendicular body composition in PD patients, provided that population-specific equations are used.

Cross-calibration of eight-polar bioelectrical impedance analysis versus dual-energy X-ray absorptiometry for the assessment of total and appendicular body composition in healthy subjects aged 21-82 years.

AIM: To calibrate eight-polar bioelectrical impedance analysis (BIA) against dual-energy X-ray absorptiometry (DXA) for the assessment of total and appendicular body composition in healthy adults. RESEARCH DESIGN: A cross-sectional study was carried out. SUBJECTS: Sixty-eight females and 42 males aged 21-82 years participated in the study. METHODS: Whole-body fat-free mass (FFM) and appendicular lean tissue mass (LTM) were measured by DXA; resistance (R) of arms, trunk and legs was measured by eight-polar BIA at frequencies of 5, 50, 250 and 500 kHz; whole-body resistance was calculated as the sum R of arms, trunk and legs. RESULTS: The resistance index (RI), i.e. the height(2)/resistance ratio, was the best predictor of FFM and appendicular LTM. As compared with weight (Wt), RI at 500 kHz explained 35% more variance of FFM (vs 0.57), 45% more variance of LTM(arm) (vs 0.48) and 36% more variance of LTM(leg) (vs 0.50) (p < 0.0001 for all). The contribution of age to the unexplained variance of FFM and appendicular LTM was nil or negligible and the RI x sex interactions were either not significant or not important on practical grounds. The percent root mean square error of the estimate was 6% for FFM and 8% for LTM(arm) and LTM(leg). CONCLUSION: Eight-polar BIA offers accurate estimates of total and appendicular body composition. The attractive hypothesis that eight-polar BIA is influenced minimally by age and sex should be tested on larger samples including younger individuals.

Accuracy of an eight-point tactile-electrode impedance method in the assessment of total body water.

OBJECTIVE: To establish the accuracy of an eight-polar tactile-electrode impedance method in the assessment of total body water (TBW). DESIGN: Transversal study. SETTING: University department. SUBJECTS: Fifty healthy subjects (25 men and 25 women) with a mean (s.d.) age of 40 (12) y. METHODS: TBW measured by deuterium oxide dilution; resistance (R) of arms, trunk and legs measured at frequencies of 5, 50, 250 and 500 kHz with an eight-polar tactile-electrode impedance-meter (InBody 3.0, Biospace, Seoul, Korea). RESULTS: An algorithm for the prediction of TBW from the whole-body resistance index at 500 kHz (height (2)/R(500) where R is the sum of the segmental resistances of arms, trunk and legs) was developed in a randomly chosen subsample of 35 subjects. This algorithm had an adjusted coefficient of determination (r2(adj)) of 0.81 (P<0.0001) and a root mean square error (RMSE) of 3.6 l (9%). Cross-validation of the predictive algorithm in the remaining 15 subjects gave an r2(adj) of 0.87 (P<0.0001) and an RMSE of 3.0 l (8%). The precision of eight-polar BIA, determined by measuring R three times a day for five consecutive days in a fasting subject, was < or =2.8% for all segments and frequencies. CONCLUSION: Eight-polar BIA is a precise method that offers accurate estimates of TBW in healthy subjects. This promising method should undergo further studies of precision and its accuracy in assessing extracellular water and appendicular body composition should be determined. SPONSORSHIP: Modena and Reggio Emilia University.

Natural history of nutrition in chronic renal failure.

Dietetic manipulation significantly influences the progression of renal failure in laboratory animals. Clinical results in humans are contradictory. The aim of the study was epidemiological research on a large sample of kidney disease patients to verify whether renal failure influences nutrient intake before dietetic manipulation. Four hundred and forty-one consecutive, non-selected adult patients with renal insufficiency (creatinine 133-963 mumol, mean 301 +/- 178 mumol in male, 288 +/- 156 mumol/l in female) and 43 kidney disease patients without renal failure were enrolled in the prospective study in the period 1988-1995. Interview at the time of the first nephrological check was performed by only one dietician; the record by recall of intake over 7 days with quantitative assessment was collected with the assistance of nutritional dossier and photographic measures. The patients with renal failure consume energy, proteins, lipids and carbohydrates in lesser quantities than the national population of the same geographical area, but the total lipid and monounsaturated fatty acid intake is higher compared with Italian dietary reference values. In patients with renal failure mean protein intake was 1.02 +/- 0.2 g/kg/day in males and 0.96 +/- 0.2 g/kg/day in females; mean lipid intake was 1.10 +/- 0.2 g/kg/day in males and 1.17 +/- 0.3 g/kg/day in females; mean carbohydrate intake was 3.7 +/- 1.1 g/kg/day in males and 3.49 +/- 1 g/kg/day in females. The nutrition alterations observed in chronic renal failure may be a biological adaptation due to neurological changes affecting the sense of taste.