The role of lean body mass as a nutritional index in Chinese peritoneal dialysis patients--comparison of creatinine kinetics method and anthropometric method.

OBJECTIVE To compare, in Chinese continuous ambulatory peritoneal dialysis (CAPD) patients, the creatinine kinetics method (LBM-CK) and the anthropometric method (LBM-AM) for determining lean body mass (LBM). DESIGN Single-center cross-sectional study. PATIENTS AND METHODS We studied 151 unselected CAPD patients (78 males, 73 females). We calculated LBM-CK and LBM-AM using standard formulas. The results of the two methods were then compared by the Bland and Altman method. Dialysis adequacy and other nutritional indices, including total Kt/V, weekly creatinine clearance (CCr), residual glomerular filtration rate (GFR), protein nitrogen appearance (PNA), subjective global assessment (SGA), and serum albumin, were measured simultaneously. RESULTS The mean age of the patients was 55.6 +/- 12.2 years, and the mean duration of dialysis was 33.6 +/- 28.5 months. The mean body mass index (BMI) was 22.7 +/- 3.7. The average LBM-AM was 43.6 +/- 8.0 kg; the average LBM-CK was 33.0 +/- 9.3 kg. The difference between the calculated LBM-AM and LBM-CK was 10.7 kg, with LBM-AM always giving a higher value; the limits of agreement were -5.8 kg and 27.1 kg. The difference between the two measures correlated with residual GFR (Pearson r = 0.629, p < 0.001). After normalizing for desired body weight, LBM-AM was only modestly correlated with serum albumin level. No correlations were found between overall SGA score or normalized protein nitrogen appearance (nPNA) and LBM-AM or LBM-CK. CONCLUSIONS In Chinese patients at least, a substantial discrepancy exists between LBM-AM and LBM-CK. The difference is especially marked in patients with significant residual renal function. The optimal method for determining LBM remains obscure in Chinese CAPD patients. Moreover, LBM correlated poorly with other nutritional indices. Multiple parameters should be taken into consideration in an assessment of nutritional status of CAPD patients.