Abstract：
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.
CONCLUSIONS: 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.
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.
CONCLUSIONS: 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.
摘要：
目的：营养不良在肾衰竭患者中非常普遍。由于体重不能反映身体成分，需要其他方法来确定肌肉质量，通常通过无脂质量（FFM）估计。生物阻抗谱（BIS）经常用于监测肾衰竭患者的身体成分。不幸的是,BIS来源的瘦组织质量（LTMBIS）不适合与FFM诊断营养不良的临界值进行比较。或计算膳食蛋白质需求。假设，FFM可以从BIS数据(FFMBIS)导出。本研究旨在将FFMBIS和LTMBIS与计算机断层扫描（CT）衍生的FFM（FFMCT）进行比较。其次，我们旨在探讨使用不同方法对计算蛋白质需求的影响。
方法：在L3水平分析60例CKD4-5期患者的CT扫描肌肉横截面积，转换为FFMCT。计算Spearman等级相关系数和95％一致极限（LoA）以比较FFMBIS和LTMBIS与FFMCT。根据FFMCT确定饮食蛋白质需求，FFMBIS和调整体重。超过10%的偏差被认为是临床相关的。
结果：FFMCT与FFMBIS相关性最强（r=0.78，p<0.001），男性（r=0.72，p<0.001）和女性（r=0.60，p<0.001）。FFMBIS和FFMCT之间的平均差为-0.54kg（LoA：-14.88至13.7kg，p=0.544)。在LTMBIS和FFMCT之间，-12.2kg的平均差很明显（LoA：-28.7至4.2kg，p<0.001)。使用FFMCT作为参考，FFMBIS最佳预测蛋白质需求。根据FFMBIS和FFMCT的蛋白质需求之间的平均差异在男性中为-0.7±9.9克，在女性中为-0.9±10.9克。
结论：FFMBIS在群体水平上与FFMCT有很好的相关性，但个体内部仍然存在很大差异。不出所料,在计算的蛋白质需求中观察到较大的临床相关差异.
方法：在L3水平分析60例CKD4-5期患者的CT扫描肌肉横截面积，转换为FFMCT。计算Spearman等级相关系数和95％一致极限（LoA）以比较FFMBIS和LTMBIS与FFMCT。根据FFMCT确定饮食蛋白质需求，FFMBIS和调整体重。超过10%的偏差被认为是临床相关的。
结果：FFMCT与FFMBIS相关性最强（r=0.78，p<0.001），男性（r=0.72，p<0.001）和女性（r=0.60，p<0.001）。FFMBIS和FFMCT之间的平均差为-0.54kg（LoA：-14.88至13.7kg，p=0.544)。在LTMBIS和FFMCT之间，-12.2kg的平均差很明显（LoA：-28.7至4.2kg，p<0.001)。使用FFMCT作为参考，FFMBIS最佳预测蛋白质需求。根据FFMBIS和FFMCT的蛋白质需求之间的平均差异在男性中为-0.7±9.9克，在女性中为-0.9±10.9克。
结论：FFMBIS在群体水平上与FFMCT有很好的相关性，但个体内部仍然存在很大差异。不出所料,在计算的蛋白质需求中观察到较大的临床相关差异.
