Estimation of lean body mass by creatinine kinetics increases the prevalence of muscle wasting in peritoneal dialysis patients compared to bioimpedance

Dialysis patients are at increased risk for muscle wasting, and time efficient screening tests are required for to allow for early detection. Creatinine kinetics have been advocated to estimate lean body mass (LBM) in peritoneal dialysis (PD) patients, and can be readily calculated in clinical practice from peritoneal dialysate effluent and urine collections. Bioimpedance is increasingly available, and we compared methods in 434 PD patients (55% men, 33.3% diabetics), mean age 55.2 +/- 16.2 years. LBM was lower by creatinine kinetics (47.8 +/- 16.6 kg men, 37.8 +/- 11.2 kg women) vs. bioimpedance (53.2 +/- 11.5 kg men, 39.2 +/- 7.2 kg women), p < 0.01. The prevalence of muscle wasting was much greater using creatinine kinetics (72.4% men, 52.4% women) vs. bioimpedance (55.2% men, 37.3%), p < 0.05. Estimates of LBM were much lower using creatinine kinetics compared to bioimpedance. Studies reporting the prevalence of muscle loss in PD patients will differ depending upon the method used to estimate muscle mass.