ASSESSMENT OF TOTAL-BODY WATER AND LEAN BODY-MASS FROM ANTHROPOMETRY,WATSON FORMULA, CREATININE KINETICS, AND BODY ELECTRICAL-IMPEDANCE COMPARED WITH ANTIPYRINE KINETICS IN PERITONEAL-DIALYSIS PATIENTS

Background. Indirect methods such as anthropometry (A), Watson formula (W), creatinine kinetics (CK), and body electrical impedance (BEI) ar e increasingly applied to determine total body water (TBW) and lean bo dy mass (LBM) in dialysis patients. These methods share the disadvanta ge that they have been validated for healthy men only. We studied whic h of these four commonly applied methods can best be used routinely in CAPD patients. Methods, TBW estimates obtained from A, W, CK, and BEI were compared with those obtained by a gold standard (antypirine dist ribution volume, ADV) in eight CAPD patients. In addition, several BEI equations to derive lean body mass (LBM) were compared with LBM estim ated by ADV in order to determine which equation is the most valuable for the assessment of LBM by BEI in CAPD patients. Results. TBW as ADV was 41.4 +/- 6.6 (mean +/- SD) L. TBW estimated by W, A and CK undere stimated ADV by a mean +/- SD of 2.3 +/- 13, 5 +/- 8.4 and 12.3 +/- 10 .9% respectively. TBW as measured by BEI overestimated ADV by 2.5 +/- 8.8%. The correlation coefficients between ADV-TBW and TBW estimated b y the indirect methods were r = 0.88 (A), r = 0.87 (BEI), r = 0.82 (CK ), and 0.68 (W). LBM estimated by ADV was 56.7 +/- 8.8 (mean +/- SD)kg ; LBM by different BEI equations ranged from 49.9 +/- 7 to 58.1 +/- 10 .7 kg. The correlation coefficient between LBM by ADV and LBM accordin g to the various BEI equations ranged from 0.81 to 0.93. Conclusion, A and BEI: can be used to estimate TBW, but the considerable SD (or ina ccuracy) makes individual predictions hazardous. Considering the corre lation coefficients and difference between LBM by ADV and LBM accordin g to different BEI equations, Deurenberg's formula can be advocated fo r use in the estimation of LBM by BEI.