Nephrol Dial Transplant (2003) 18: 1943-1944
© 2003 European Renal Association-European Dialysis and Transplant Association
Letter and Reply
Bioelectrical impedance analysis and assessment of body composition in end-stage renal disease
1 Unità Operativa di Nefrologia e Dialisi Ospedale ‘A. Landolfi’ Solofra, ASL AV/22 Unità Operativa di Nefrologia e Dialisi Ospedale ‘Curto’ Polla, ASL SA/3 Italy Email: bidiior{at}tin.it
Sir,
We read with interest the paper of Kamimura et al. [1] concerning the comparison of skinfold thickness (ST), bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DEXA) for the assessment of body fat in chronic haemodialysis patients. The authors concluded that in haemodialysis ST is preferable to BIA, because of the lower gender-specific variability in the assessment of body fat. Nonetheless, due to its simplicity, BIA has received much attention from nephrologists; it has been suggested that BIA would be preferable to ST due to the more precise evaluation of hydration status and to the lower inter-operator error [1].
We would like to raise some questions. Is it more relevant for haemodialysis patients to measure obesity or malnutrition? Malnutrition is well measurable with techniques other than ST, including BIA. Indeed, in haemodialysis the BIA-derived phase angle correlates with mortality [2–4]. On the contrary, the association between ST and mortality in haemodialysis has never been described.
Is it more relevant in haemodialysis to measure body fat, or total body water? BIA correlates with the water content of the subject and is well used to evaluate the hydration state in both stable and unstable haemodialysis patients [5]. Moreover, norms for BIA variables in haemodialysis have been described [6]. On the contrary, norms of ST in haemodialysis have never been reported.
What is the most reliable time for measuring body water in haemodialysis? As subjects on haemodialysis undergo cyclical variations of body water content, it would be useful to standardize the timing of BIA measurements; in other words, does a phenomenon of electric post-haemodialysis rebound exist? Twenty-seven patients on long-term haemodialysis underwent BIA measurements at the beginning, the end, 15, 30, 60, 90 and 120 min and 24, 48 and 72 h after the end of the haemodialysis session. Dialysis de-hydration measured 2.8 l; body weight increased by 1.4, 2.6 and 3.4 l at the 24, 48, 68 h time. R and Xc significantly changed during dialysis (R 453 ± 74 to 542 ± 98, P < 0.05; Xc 38 ± 10, 53 ± 16, P < 0.05) and during the interdialysis period (R 471 ± 79, 429 ± 98 and 424 ± 68, P < 0.05; Xc 42 ± 13, 37 ± 10 and 34 ± 13, P < 0.05); alternatively, R and Xc were absolutely stable during the 2-h post-dialysis time. The data suggest that BIA measurements can be performed anytime after the haemodialysis session, as they are not influenced by post-haemodialysis fluid re-equilibrium.
Of note, any condition associated with hydration abnormalities, like haemodialysis, introduces a distortion in the water compartments, with unpredictable propagation of the error in the assessment of body water performed with whatever technique. In fact, post-dialysis DEXA finds evidence of a reduction of both fat free mass and body density, and ST reduces the FFM by 5% [7].
In summary, in haemodialysis BIA is a simple, reproducible, non operator-dependent method for estimating total body water and can be used as a predictor of survival. BIA is not capable of estimating the adiposity in haemodialysis patients, but such measure seems to be less relevant in this population.
Conflict of interest statement. None declared.
References
- Kamimura MA, Avesani CM, Cendoroglo M, Canziani MEF, Draibe SA, Cuppari L. Comparison of skinfold thickness and bioelectrical impedance analysis with dual-energy X-ray absorptiometry for the assessment of body fat in patients on long-term haemodialysis therapy. Nephrol Dial Transplant 2003; 18: 101–105
[Abstract/Free Full Text] - Maggiore Q, Nigrelli S, Ciccarelli C, Grimaldi C, Red GA, Michelassi C. Nutritional and prognostic correlates of bioimpedance indexes in hemodialysis patients. Kidney Int 1996; 50: 2103–2108[Medline]
- Chertow GM, Jacobs D, Lazarus JM, et to the: Phase angle predicts survival in hemodialysis patients. J Renal Nutr 1997; 7: 204–207
- Di Iorio B, Terracciano V, Querques M et al. Bioimpedance indexes predict survival in hemodialysis patients. J Renal Nutr 1997; 7: 216–217
- Piccoli A, for the Italian Hemodialysis-Bioelectrical Impedance Analysis Study Group. Identification of operational clues to dry weight prescription in hemodialysis using bioimpedance vector analysis. Kidney Int 1998; 53: 1036–1043[CrossRef][Web of Science][Medline]
- Chertow GM, Lazarus JM, Lew NL But NL, Lowrie EG. Bioimpedance norms for the hemodialysis population. Kidney Int 1997; 52: 1617–1621[Medline]
- Abrahamsen B, Hansen TB, Pedersen FB, Beck-Nielsen H. Impact oh hemodialysis on DEXA, BIA, and anthropometry. Am J Clin Nutr 1996; 63: 80–86
[Abstract/Free Full Text]
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