Department of Clinical and Molecular Medicine, La Sapienza University, Rome, Italy.
Nephrol Dial Transplant. 2011 Dec;26(12):3950-4. doi: 10.1093/ndt/gfr140. Epub 2011 Mar 25.
Measurement of urinary albumin excretion (UAE) shows important intra-individual variability suggesting the need for multiple assessments. This study aimed at investigating the reproducibility of UAE in type 2 diabetes.
UAE was obtained from two to three samples collected in a 3- to 6-month period from 4062 of the 15 773 type 2 diabetic subjects participating in the Renal Insufficiency And Cardiovascular Events (RIACE) Italian Multicentre Study in 2007-08. UAE was assessed as albumin excretion rate (AER) in 24-h urine collections from 833 subjects and albumin:creatinine ratio (A/C) in early-morning urine samples from 3229 patients. Albuminuria was measured by immunonephelometry or immunoturbidimetry.
The median coefficient of variation (CV) was 32.5% (interquartile range: 14.3-58.9). Concordance rate between a single UAE and the geometric mean of multiple measurements was 94.6% for normoalbuminuria, 83.5% for microalbuminuria, 91.1% for macroalbuminuria and 90.6% for albuminuria (micro + macro). CV was significantly higher (P < 0.01) for AER measurement than for A/C and with immunoturbidimetry than with immunonephelometry, whereas concordance rates were similar between the two modalities of urine collection and the two assay methods. Receiver-operating characteristic (ROC) plots demonstrated a good performance of single UAE in predicting the geometric mean of multiple measures at the cut-off level of both microalbuminuria (ROC(AUC) 0.926; 95% confidence interval: 0.915-0.937) and macroalbuminuria (ROC(AUC) 0.950; 95% confidence interval: 0.927-0.973).
Data from this large cohort indicate that, in type 2 diabetic subjects, a single UAE value, thought to be encumbered with high intra-individual variability, is an accurate predictor of nephropathy stage for clinical and epidemiological purposes.
尿白蛋白排泄率（UAE）的测量显示出重要的个体内变异性，这表明需要多次评估。本研究旨在探讨 2 型糖尿病患者 UAE 的可重复性。
在 2007-08 年，来自参加肾脏不足和心血管事件（RIACE）意大利多中心研究的 15773 名 2 型糖尿病患者中的 4062 名患者在 3-6 个月期间采集了两到三份尿液样本，以获得 UAE。从 833 名患者中采集 24 小时尿液样本，以白蛋白排泄率（AER）评估 UAE，从 3229 名患者中采集晨尿样本，以白蛋白：肌酐比值（A/C）评估 UAE。白蛋白尿通过免疫比浊法或免疫散射比浊法测量。
中位变异系数（CV）为 32.5%（四分位间距：14.3-58.9）。对于正常白蛋白尿，单次 UAE 与多次测量的几何平均值之间的一致性率为 94.6%，对于微量白蛋白尿为 83.5%，对于大量白蛋白尿为 91.1%，对于白蛋白尿（微量+大量）为 90.6%。AER 测量的 CV 明显高于 A/C（P<0.01），免疫比浊法的 CV 明显高于免疫散射比浊法，而两种尿液收集方式和两种检测方法之间的一致性率相似。受试者工作特征（ROC）曲线表明，在微量白蛋白尿的截断值（ROC（AUC）0.926；95%置信区间：0.915-0.937）和大量白蛋白尿的截断值（ROC（AUC）0.950；95%置信区间：0.927-0.973）水平下，单次 UAE 能够很好地预测多次测量的几何平均值。
本大型队列研究的数据表明，在 2 型糖尿病患者中，单次 UAE 值被认为具有较高的个体内变异性，但对于临床和流行病学目的来说，它是一种准确预测肾病分期的指标。
