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Lean Mass Estimation by Creatinine Kinetics and Dual-Energy X-Ray Absorptiometry in Peritoneal Dialysis

Background: Malnutrition is widely prevalent in dialysis. Malnourished patients present depletion of somatic protein stores and a decrease in lean body mass (LBM) that can be measured by different techniques. Aims: (1) To assess the reliability of lean mass measurements obtained by creatinine kinetics (CrK) in a group of stable peritoneal dialysis (PD) patients, using dual-energy x-ray absorptiometry (DEXA) measurements as the reference method; (2) to establish the reproducibility of LBM estimated by CrK in individual patients analyzing repeated measurement in the short term, and (3) to correlate measurements of LBM with laboratory determinations that assess nutritional status. Methods: We performed a cross-sectional evaluation of LBM by DEXA and CrK in 39 PD patients. In 14 patients we performed repeated measurements of LBM by CrK in the short term. Results: No significant difference was found in mean lean mass values estimated by both methods: mean DEXA LBM was 41.7 kg, 36.1 ± 4.5 kg in females and 52.7 ± 6.4 kg in males and mean CrK LBM was 41.08 kg, 37.5 ± 6.1 kg in females and 48.1 ± 8.4 kg in males. A good correlation was found between both techniques (r = 0.71; p < 0.003). The mean difference between the two methods was 0.638 ± 6.95 kg (95% confidence limits: –12.98 and +14.26). A wide scatter of the differences between both methods was seen throughout the range of measurements of LBM. When LBM by CrK was repeatedly (2–3 times) measured in a period of 3–4 months in 14 patients, it had a coefficient of variation (CV) of 15.39% (range 2.89–42.88%), while body weight CV in the same period was 0.69% (range 0–1.9%). Conclusions: CrK is an unsatisfactory method for the assessment of LBM in PD patients.