Kurutas Ergul Belge, Gumusalan Yakup, Cetinkaya Ali, Dogan Ekrem
Department of Biochemistry, Sutcu Imam University Faculty of Medicine, Avsar Campus, 46050 Kahramanmaras, Turkey.
Department of Anatomy, Fatih University Faculty of Medicine, Büyükçekmece Campus, 34500 Istanbul, Turkey.
Biol Proced Online. 2015 Feb 2;17(1):3. doi: 10.1186/s12575-015-0015-9. eCollection 2015.
Oxidative stress biomarkers such as superoxide dismutase (CuZnSOD), catalase (CAT) and malondialdehyde (MDA) play an important role in the pathogenesis or progression of numerous diseases. Data regarding the biological variation and analytical quality specifications (imprecision, bias and total error) for judging the acceptability of method performance for oxidative stress biomarkers in urine are conspicuously lacking in the literature. Such data are important in setting analytical quality specifications, assessing the utility of population reference intervals (index of individuality) and assessing the significance of changes in serial results from an individual (reference change value; RCV).
20 patients with type 2 diabetes mellitus (T2DM), 20 patients with diabetic nephropathy (DN) and 14 healthy individuals as control were involved in this study. Timed first morning urine samples were taken from patients and healthy groups on the zero, 1st, 3rd, 5th, 7th, 15th and 30th days. Index of individuality and reference change value were calculated from within-subject and between-subject variations. Methods of oxidative stress biomarkers in human blood were adopted in human urine and markers were measured as spectrophotometrically. Also, analytical quality specifications for evaluation of the method performance were established for oxidative stress biomarkers in urine.
Within-subject variations of oxidative stress biomarkers were significantly higher in patients with DN and T2DM compared to healthy subjects. MDA showed low individuality, and within-subject variances of MDA were larger than between-subject variances in all groups. However, CAT and CuZnSOD showed strong individuality, but within-subject variances of them were smaller than between-subject variances in all groups. RCVs of all analytes in diabetic patients were relatively higher, because of high within-subject variation, resulting in a higher RCV. Also, the described methodology achieves these goals, with analytical CVs of < 3.5% for all analytes. Goals for bias and total error were 6.0-7.9% and 12.5-23.3%, respectively.
RCVs concept for predicting the clinical status in diabetic patients represents an optimization of laboratory reporting and could be a valuable tool for clinical decision. Furthermore, for oxidative stress biomarkers' measurements in urine, the desirable imprecision goals based on biological variation are obtainable by current methodologies.
超氧化物歧化酶（铜锌超氧化物歧化酶）、过氧化氢酶和丙二醛等氧化应激生物标志物在众多疾病的发病机制或进展中发挥着重要作用。关于尿液中氧化应激生物标志物方法性能可接受性的生物学变异和分析质量规范（不精密度、偏倚和总误差）的数据在文献中明显缺乏。这些数据对于设定分析质量规范、评估人群参考区间（个体指数）的效用以及评估个体连续结果变化的意义（参考变化值；RCV）很重要。
本研究纳入20例2型糖尿病（T2DM）患者、20例糖尿病肾病（DN）患者和14名健康个体作为对照。在第0、1、3、5、7、15和30天从患者和健康组采集定时首次晨尿样本。根据受试者内和受试者间变异计算个体指数和参考变化值。将人体血液中氧化应激生物标志物的方法应用于人体尿液，并通过分光光度法测量标志物。此外，还建立了尿液中氧化应激生物标志物方法性能评估的分析质量规范。
与健康受试者相比，DN和T2DM患者氧化应激生物标志物的受试者内变异显著更高。MDA个体性较低，且MDA的受试者内方差在所有组中均大于受试者间方差。然而，CAT和铜锌超氧化物歧化酶个体性较强，但它们的受试者内方差在所有组中均小于受试者间方差。由于受试者内变异较高，糖尿病患者所有分析物的RCV相对较高，导致RCV较高。此外，所描述的方法实现了这些目标，所有分析物的分析CV均<3.5%。偏倚和总误差的目标分别为6.0 - 7.9%和12.5 - 23.3%。
用于预测糖尿病患者临床状态的RCV概念代表了实验室报告的优化，可能是临床决策的有价值工具。此外，对于尿液中氧化应激生物标志物的测量，基于生物学变异的理想不精密度目标可通过当前方法实现。
