Fat-Free Mass Derived From Bioimpedance Spectroscopy and Computed Tomography are in Good Agreement in Patients With Chronic Kidney Disease.

OBJECTIVE: Malnutrition is highly prevalent in patients with kidney failure. Since body weight does not reflect body composition, other methods are needed to determine muscle mass, often estimated by fat-free mass (FFM). Bioimpedance spectroscopy (BIS) is frequently used for monitoring body composition in patients with kidney failure. Unfortunately, BIS-derived lean tissue mass (LTMBIS) is not suitable for comparison with FFM cutoff values for the diagnosis of malnutrition, or for calculating dietary protein requirements. Hypothetically, FFM could be derived from BIS (FFMBIS). This study aims to compare FFMBIS and LTMBIS with computed tomography (CT) derived FFM (FFMCT). Secondarily, we aimed to explore the impact of different methods on calculated protein requirements. METHODS: CT scans of 60 patients with kidney failure stages 4-5 were analyzed at the L3 level for muscle cross-sectional area, which was converted to FFMCT. Spearman rank correlation coefficient and 95% limits of agreement were calculated to compare FFMBIS and LTMBIS with FFMCT. Protein requirements were determined based on FFMCT, FFMBIS, and adjusted body weight. Deviations over 10% were considered clinically relevant. RESULTS: FFMCT correlated most strongly with FFMBIS (r = 0.78, P < .001), in males (r = 0.72, P < .001) and in females (r = 0.60, P < .001). A mean difference of -0.54 kg was found between FFMBIS and FFMCT (limits of agreement: -14.88 to 13.7 kg, P = .544). Between LTMBIS and FFMCT a mean difference of -12.2 kg was apparent (limits of agreement: -28.7 to 4.2 kg, P < .001). Using FFMCT as a reference, FFMBIS best predicted protein requirements. The mean difference between protein requirements according to FFMBIS and FFMCT was -0.7 ± 9.9 g in males and -0.9 ± 10.9 g in females. CONCLUSION: FFMBIS correlates well with FFMCT at a group level, but shows large variation within individuals. As expected, large clinically relevant differences were observed in calculated protein requirements.

The Impact of Combined Nutrition and Exercise Interventions in Patients with Chronic Kidney Disease.

Combined nutrition and exercise interventions potentially improve protein-energy wasting/malnutrition-related outcomes in patients with chronic kidney disease (CKD). The aim was to systematically review the effect of combined interventions on nutritional status, muscle strength, physical performance and QoL. MEDLINE, Cochrane, Embase, Web of Science and Google Scholar were searched for studies up to the date of July 2023. Methodological quality was appraised with the Cochrane risk-of-bias tool. Ten randomized controlled trials (nine publications) were included (334 patients). No differences were observed in body mass index, lean body mass or leg strength. An improvement was found in the six-minute walk test (6-MWT) (n = 3, MD 27.2, 95%CI [7 to 48], p = 0.008), but not in the timed up-and-go test. No effect was found on QoL. A positive impact on 6-MWT was observed, but no improvements were detected in nutritional status, muscle strength or QoL. Concerns about reliability and generalizability arise due to limited statistical power and study heterogeneity of the studies included.