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 electricalimpedance (BEI) are increasingly applied to determine total body water(TBW) and lean body mass (LBM) in dialysis patients. These methods sharethe disadvantage that they have been validated for healthy men only. Westudied which of these four commonly applied methods can best be usedroutinely in CAPD patients. Methods. TBW estimatesobtained from A, W, CK, and BEI were compared with those obtained by a goldstandard (antypirine distribution volume, ADV) in eight CAPD patients. Inaddition, several BEI equations to derive lean body mass (LBM) werecompared with LBM estimated by ADV in order to determine which equation isthe 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 underestimated ADV bya mean±SD of 2.3±13, 5±8.4 and12.3±10.9% respectively. TBW as measured by BEI overestimatedADV by 2.5±8.8%. The correlation coefficients between ADV-TBWand TBW estimated by 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±8.9(mean±SD) kg; LBM by different BEI equations ranged from49.9±7 to 58.1±10.7 kg. The correlation coefficientbetween LBM by ADV and LBM according to the various BEI equations rangedfrom 0.81 to 0.93. Conclusions. A and BEI: can be usedto estimate TBW, but the considerable SD (or inaccuracy) makes individualpredictions hazardous. Considering the correlation coefficients anddifference between LBM by ADV and LBM according to different BEI equations,Deurenberg's formula can be advocated for use in the estimation of LBM byBEI.