Lean body mass estimation by creatinine kinetics, bioimpedance, and dual energy x-ray absorptiometry in patients on continuous ambulatory peritoneal dialysis.

Lean body mass (LBM), which is fat free body mass, can be used as an index of nutritional status. We evaluated three techniques for LBM estimation, including dual energy x-ray absorptiometry (DEXA), creatinine kinetics (CrKin), and bioimpedance (BI) in 10 patients on continuous ambulatory peritoneal dialysis (CAPD). Two different formulae were applied for BI LBM estimation, Segal (S) and Deurenberg (D). Mean values (+/- SEM) of LBM estimated were 48.2 +/- 3.6, 46.12 +/- 2.87, 43.32 +/- 3.87, and 41.27 +/- 4.26 by DEXA, BI-S, BI-D, and CrKin, respectively. LBM by CrKin was significantly lower than that by DEXA and BI-S values. There was no statistically significant difference between DEXA and BI-S values. Statistically significant correlations were found between LBM values by all methods. Particularly strong correlations were found between DEXA versus BI-S (r = 0.976) and BI-S versus BI-D (r = 0.98). Because clinical assessment of hydration status is inaccurate, and both BI and DEXA measure excess extracellular water in LBM, falling muscle mass may be missed by these techniques. The CrKin technique for estimating LBM at normal body fluid volumes (dry weight) may be a better index of nutritional status in patients on CAPD because this may truly reflect the dry LBM and changes in muscle mass. Both DEXA and BI include excess body water in LBM and may mask malnutrition in the presence of subclinical or clinical overhydration, which is common in patients on peritoneal dialysis.