Miller Alistair, Strauss Boyd J, Mol Stijn, Kyoong Andrew, Holmes Peter H, Finlay Paul, Bardin Philip G, Guy Paul
Department of Respiratory and Sleep Medicine, Monash University, Melbourne, Victoria, Australia.
Respirology. 2009 Apr;14(3):411-8. doi: 10.1111/j.1440-1843.2009.01499.x.
Mortality and morbidity in COPD have been related to reduced FEV1 as well as indices of body composition. Different techniques used to evaluate body composition may vary in accuracy, particularly in conditions with altered fluid balance such as COPD. We hypothesized that direct measurement of fat-free mass index (FFMI) by dual-energy X-ray absorptiometry (DEXA) would provide superior assessment of body composition in COPD.
We measured body composition in 31 patients with COPD randomly selected from a teaching hospital clinic. To estimate total body water (TBW) and FFMI, skin-fold anthropometry, bioelectrical impedance analysis (BIA) with Schols and Lukaski equations as well as DEXA, total body potassium by whole-body gamma-counting (TBK) and in vivo neutron activation analysis were used. Combined body composition methods providing precise estimations of TBW were used for comparisons. Bland-Altman analyses, ANOVA and chi2-testing were used to examine data.
Mean BMI was 27.6 +/- 5.34 kg/m2 (mean +/- SD). Estimations of TBW were similar using Schols BIA or by using combined body composition methods. FFMI did not vary significantly between grades of COPD severity but was significantly different when assessed using DEXA and other methods. Calculated FFM hydration was significantly different from the fixed hydration factor used to calculate FFMI from BIA TBW (P < 0.05).
The Schols BIA method incorporates a fixed hydration factor that may lead to an erroneous estimation of FFMI with ensuing clinical implications. DEXA can be used to obtain accurate and comprehensive assessments of body composition and should be the preferred investigation in COPD.
慢性阻塞性肺疾病（COPD）的死亡率和发病率与第一秒用力呼气容积（FEV1）降低以及身体成分指标有关。用于评估身体成分的不同技术在准确性上可能存在差异，尤其是在诸如COPD这种伴有液体平衡改变的情况下。我们推测，通过双能X线吸收法（DEXA）直接测量去脂体重指数（FFMI）能更优地评估COPD患者的身体成分。
我们从一家教学医院诊所随机选取了31例COPD患者测量其身体成分。为估算总体水（TBW）和FFMI，使用了皮褶人体测量法、采用Schols和Lukaski公式的生物电阻抗分析（BIA）以及DEXA、通过全身γ计数法测定的总体钾（TBK）和活体中子活化分析。采用能精确估算TBW的联合身体成分方法进行比较。使用Bland-Altman分析、方差分析（ANOVA）和卡方检验来分析数据。
平均体重指数（BMI）为27.6±5.34kg/m²（均值±标准差）。使用Schols BIA法或联合身体成分方法估算的TBW相似。COPD严重程度不同等级之间的FFMI无显著差异，但使用DEXA和其他方法评估时则有显著差异。计算得出的去脂体重水合度与用于根据BIA TBW计算FFMI的固定水合因子有显著差异（P<0.05）。
Schols BIA法纳入了一个固定水合因子，这可能导致对FFMI的错误估算，进而产生临床影响。DEXA可用于准确、全面地评估身体成分，应作为COPD的首选检查方法。
