Bedogni G, Polito C, Severi S, Strano C G, Manzieri A M, Alessio M, Iovene A, Battistini N
Dipartimento di Scienze Biomediche, Università degli Studi, Modena, Italy.
Eur J Clin Nutr. 1996 Jun;50(6):335-9.
To assess the reliability of bioelectric impedance analysis (BIA) for predicting total body water (TBW) and extracellular water (ECW) in children affected by juvenile rheumatoid arthritis (JRA).
Thirty-nine children affected by JRA and 23 healthy children of similar age (11.0 +/- 3.6, range 3.0-19.0 y) were recruited for the study.
TBW and ECW were measured by deuterium oxide and bromide dilution, respectively. Bioelectric impedance (Z) was measured at frequencies of 5, 50 and 100 kHz. The prediction of TBW and ECW from BIA was based on the impedance index (ZI = height2/Z, cm2/omega).
TBW standardized per kg of body weight and ECW standardized per litre of TBW were significantly higher in JRA as compared to control patients (59.7 +/- 2.4 vs 57.7 +/- 2.7% and 44.5 +/- 4.6 vs 38.1 +/- 7.9%, with P < 0.005 and P < 0.0001, respectively). Moreover, intracellular water standardized per litre of TBW was significantly lower in JRA than in control subjects (55.5 +/- 4.6 vs 62.5 +/- 8.1, with P < 0.0001). In both controls and patients, the use of ZI at 5kHz offered the more accurate prediction of ECW. However, the use of ZI at 100 kHz did not offer a better prediction of TBW as compared to its value of 50 kHz. Control-generated formulae for predicting water compartments from BIA [TBW = 0.716 x ZI at 100 kHz-1.504, r = 0.934, s.e.e. = 2.2 l;:ECW = 0.430 x ZI5-3.652, r = 0.869(7) s.e.e. = 1.7 l] underestimated TBW and ECW in JRA patients. However, population-specific formulae [TBW (1) = 0.766 x ZI at 100 kHz-0.053, r = 0.939, s.e.e. = 2.8 l; ECW (l) = 0.399 x ZI at 5 kHz-0.283, r = 0.886, s.e.e. = 1.7 l] allowed an accurate prediction of TBW and ECW in JRA patients, taking into account their altered body water distribution.
Altered water distribution impedes the use of formulae developed on healthy children to predict TBW and ECW from BIA and JRA patients. It is hypothesized that chronic inflammation and subclinical malnutrition may be responsible for the altered body water distribution of JRA patients. Traditional body composition models may require adjustments for use in JRA children due to their altered body hydration and water distribution.
评估生物电阻抗分析（BIA）预测幼年类风湿关节炎（JRA）患儿总体水（TBW）和细胞外水（ECW）的可靠性。
招募了39名患JRA的儿童和23名年龄相仿（11.0±3.6岁，范围3.0 - 19.0岁）的健康儿童进行该研究。
分别采用氧化氘和溴化物稀释法测量TBW和ECW。在5、50和100kHz频率下测量生物电阻抗（Z）。基于阻抗指数（ZI =身高²/Z，cm²/Ω）由BIA预测TBW和ECW。
与对照患者相比，JRA患儿每千克体重标准化的TBW和每升TBW标准化的ECW显著更高（分别为59.7±2.4对57.7±2.7%以及44.5±4.6对38.1±7.9%，P分别<0.005和P<0.0001）。此外，JRA患儿每升TBW标准化的细胞内水显著低于对照受试者（55.5±4.6对62.5±8.1，P<0.0001）。在对照组和患者中，使用5kHz的ZI对ECW的预测更准确。然而，与50kHz时相比，使用100kHz的ZI对TBW的预测并未更好。根据对照组数据生成的用于由BIA预测水含量的公式[TBW = 0.716×100kHz时的ZI - 1.504，r = 0.934，标准误 = 2.2升；ECW = 0.430×ZI5 - 3.652，r = 0.869(7)，标准误 = 1.7升]低估了JRA患者的TBW和ECW。然而，针对特定人群的公式[TBW(1) = 0.766×100kHz时的ZI - 0.053，r = 0.939，标准误 = 2.8升；ECW(1) = 0.399×5kHz时的ZI - 0.283，r = 0.886，标准误 = 1.7升]考虑到JRA患者改变的身体水分分布，能够准确预测其TBW和ECW。
水分分布改变阻碍了基于健康儿童开发的公式用于由BIA预测JRA患者的TBW和ECW。据推测，慢性炎症和亚临床营养不良可能是JRA患者身体水分分布改变的原因。由于JRA儿童身体水合作用和水分分布改变，传统身体成分模型可能需要调整以用于JRA儿童。
