Borovnicar D J, Wong K C, Kerr P G, Stroud D B, Xiong D W, Strauss B J, Atkins R C
Department of Medicine, Monash University, Clayton, Melbourne, Victoria, Australia.
Eur J Clin Nutr. 1996 Sep;50(9):607-16.
To assess the usefulness of fat-free mass (FFM) as an index of total body protein (TBPr) status in continuous ambulatory peritoneal dialysis (CAPD) patients.
TBPr was measured by in vivo neutron activation analysis (IVNAA) and expressed as a standardised protein index (PI). FFM was estimated by dual energy X-ray absorptiometry (DXA), whole body counting of total body potassium (TBK), and creatinine kinetics (CK), and expressed as a standardised FFM index (FFMI). FFM was also determined by a criterion method based on four compartment model (4CM) which is defined as the sum of total body water determined by D2O dilution, TBPr determined by IVNAA, bone mineral determined by DXA, and glycogen estimated to be 4.4% of TBPr. Each patient was measured within a four hour period by all methods.
Body Composition Laboratory, Monash Medical Centre.
Six male and twelve female CAPD patients (33-77 years).
FFMI assessed by DXA and by TBK agreed with measurements of PI on identifying the mean TBPr status of the CAPD group as significantly below a comparable normal reference population (mean Z score: PI = -1.01 (P < 0.05); FFMI by DXA = -0.50 (P < 0.05); FFMI by TBK = -1.24 (P < 0.05)). In contrast, FFMI assessed by CK did not reveal a significantly reduced TBPr status (mean Z score: -0.70 (NS)). Furthermore, significant linear correlations were noted between PI and FFMI estimated by DXA and by TBK (r = 0.57 (P < 0.05) vs r = 0.69 (P < 0.05)) however no significant correlation was observed between PI and FFMI estimated by CK (r = 0.36 (NS)). Moderate variation in FFM hydration did not compromise the ability of DXA, TBK or CK to differentiate between protein deleted, normal and enriched patients. Comparison of FFM estimates between the criterion method and either DXA, TBK or CK revealed no significant bias (+ 1.8 kg vs -2.0 kg vs +0.8 kg) and respective SEE values of 3.8 kg (8.3%), 5.9 kg (14.3%) and 9.6 kg (21.7%).
The findings of this study indicate that FFM estimated by either DXA or the whole body counting of TBK is a useful index of TBPr status in CAPD patients. However, FFM assessed by CK does not appear to be an appropriate index of TBPr status in CAPD patients.
评估无脂肪体重（FFM）作为持续性非卧床腹膜透析（CAPD）患者全身蛋白质（TBPr）状态指标的实用性。
通过体内中子活化分析（IVNAA）测量TBPr，并表示为标准化蛋白质指数（PI）。通过双能X线吸收法（DXA）、全身钾计数（TBK）和肌酐动力学（CK）估算FFM，并表示为标准化FFM指数（FFMI）。FFM也通过基于四室模型（4CM）的标准方法确定，该模型定义为通过重水稀释测定的全身水、通过IVNAA测定的TBPr、通过DXA测定的骨矿物质以及估计为TBPr的4.4%的糖原之和。所有方法在4小时内对每位患者进行测量。
莫纳什医疗中心人体成分实验室。
6名男性和12名女性CAPD患者（33 - 77岁）。
通过DXA和TBK评估的FFMI在识别CAPD组的平均TBPr状态显著低于可比正常参考人群方面与PI测量结果一致（平均Z评分：PI = -1.01（P < 0.05）；通过DXA的FFMI = -0.50（P < 0.05）；通过TBK的FFMI = -1.24（P < 0.05））。相比之下，通过CK评估的FFMI未显示TBPr状态显著降低（平均Z评分：-0.70（无显著性差异））。此外，PI与通过DXA和TBK估算的FFMI之间存在显著线性相关性（r = 0.57（P < 0.05）对r = 0.69（P < 0.05）），然而PI与通过CK估算的FFMI之间未观察到显著相关性（r = 0.36（无显著性差异））。FFM水合作用中等程度的变化并未损害DXA、TBK或CK区分蛋白质缺乏、正常和蛋白质丰富患者的能力。标准方法与DXA、TBK或CK之间的FFM估计值比较显示无显著偏差（分别为 +1.8 kg对 -2.0 kg对 +0.8 kg），相应的标准误估计值分别为3.8 kg（8.3%）、5.9 kg（14.3%）和9.6 kg（21.7%）。
本研究结果表明，通过DXA或TBK全身计数估算的FFM是CAPD患者TBPr状态的有用指标。然而, 通过CK评估的FFM似乎不是CAPD患者TBPr状态合适的指标。
