Iacone Roberto, D'Elia Lanfranco, Guida Bruna, Barbato Antonio, Scanzano Clelia, Strazzullo Pasquale
Department of Clinical Medicine and Surgery, Federico II University Medical School, Naples, Italy.
J Clin Lab Anal. 2018 Jul;32(6):e22407. doi: 10.1002/jcla.22407. Epub 2018 Feb 9.
Twenty-four-hour urinary creatinine excretion (24hUCrE) is strongly correlated with skeletal muscle mass (SMM). This study suggests how to exploit the power of the SMM-24hUCrE correlation to assess the accuracy of 24hUCrE measurement.
Four hundred and sixty-six men, a subgroup of participants in the 2002-2004 follow-up examination of the Olivetti Heart Study, performed a 24-h urine collection to measure 24hUCrE and underwent bioelectrical impedance analysis to evaluate SMM. Linear regression analysis between 24hUCrE and SMM was used to calculate the muscle-creatinine equivalence and to develop an equation to predict the 24hUCrE depending on SMM. The accuracy of the 24hUCrE measurement was assessed using the change in the SMM-24hUCrE correlation coefficient upon variation in the percentage deviation (%D) between the measured and predicted 24hUCrE.
The calculated muscle-creatinine equivalence was 1 g of 24hUCrE = 22.73 kg of SMM. The %Ds and the corresponding SMM-24hUCrE correlation coefficients were as follows: %D = 3.0, r = .997; %D = 4.7, r = .989; %D = 8.1, r = .963; %D = 10.5, r = .940; %D = 12.6, r = .909; %D = 18.9, r = .825; %D = 25.8, r = .707; %D = 33.5, r = .595; %D = 41.4, r = .453.
The increase in %D corresponds to a reduced correlation between muscle mass and creatinine excretion, which indicated a poor performance in the measurement of the 24hUCrE. For studies on single individuals, where small variations in 24hUCrE could be significant, a %D up to 12.6% is suggested; on the other hand, a wider %D interval could be acceptable for population studies.
24小时尿肌酐排泄量（24hUCrE）与骨骼肌质量（SMM）密切相关。本研究提出如何利用SMM与24hUCrE之间的相关性来评估24hUCrE测量的准确性。
466名男性，他们是奥利维蒂心脏研究2002 - 2004年随访检查参与者的一个亚组，进行了24小时尿液收集以测量24hUCrE，并接受生物电阻抗分析以评估SMM。使用24hUCrE与SMM之间的线性回归分析来计算肌肉 - 肌酐当量，并建立一个根据SMM预测24hUCrE的方程。通过测量的和预测的24hUCrE之间的百分比偏差（%D）变化时SMM - 24hUCrE相关系数的变化来评估24hUCrE测量的准确性。
计算出的肌肉 - 肌酐当量为1克24hUCrE = 22.73千克SMM。%D值及其对应的SMM - 24hUCrE相关系数如下：%D = 3.0，r = 0.997；%D = 4.7，r = 0.989；%D = 8.1，r = 0.963；%D = 10.5，r = 0.940；%D = 12.6，r = 0.909；%D = 18.9，r = 0.825；%D = 25.8，r = 0.707；%D = 33.5，r = 0.595；%D = 41.4，r = 0.453。
%D的增加对应于肌肉质量与肌酐排泄之间相关性的降低，这表明24hUCrE测量的性能较差。对于个体研究，其中24hUCrE的小变化可能很显著，建议%D高达12.6%；另一方面，对于人群研究，更宽的%D区间可能是可接受的。
