Comparing bioimpedance spectrometry and traditional creatinine kinetics methods for the assessment of muscle mass in peritoneal dialysis patients.

Background: Sarcopenia is a common and serious problem in patients receiving peritoneal dialysis (PD). Lean tissue mass (LTM) by bioimpedance spectrometry is a reasonably accurate method for measuring muscle mass. Fat-free edema-free body mass (FEBM) as determined by the creatinine kinetics method is a traditional method but evidence to support its use is limited.

Methods: We studied 198 new PD patients. Their serial LTM and FEBM were reviewed and compared by the Bland and Altman method. Multi-variable regression model was used to determine factors associated with the disparity between the two methods.

Results: There was a significant but moderate correlation between LTM and FEBM (r = 0.309, P < .0001). LTM was consistently higher than FEBM, with an average difference 13.98 kg (95% confidence interval -5.90 to 33.86 kg), and the difference strongly correlated with LTM (r = 0.781, P < .0001). By multivariable linear regression analysis, LTM and residual renal function were independent predictors of the LTM-FEBM difference. Where the measurements were repeated in 12 months, there was no significant correlation between ∆LTM and ∆FEBM (r = -0.031, P = .799).

Conclusion: There is a significant difference between LTM and FFBM. This discrepancy correlated with LTM and residual renal function, highlighting the limitations of FFBM in assessing skeletal muscle mass.