冷冻方法会影响尿蛋白的浓度和变异性以及微量白蛋白尿数据的解读。牛津地区前瞻性研究小组。

Freezing method affects the concentration and variability of urine proteins and the interpretation of data on microalbuminuria. The Oxford Regional Prospective Study Group.

作者信息

Schultz C J, Dalton R N, Turner C, Neil H A, Dunger D B

机构信息

Division of Public Health and Primary Health Care, Institute of Health Sciences, University of Oxford, UK.

出版信息

Diabet Med. 2000 Jan;17(1):7-14. doi: 10.1046/j.1464-5491.2000.00200.x.

DOI:10.1046/j.1464-5491.2000.00200.x

PMID:10691153

Abstract

AIMS

Microalbuminuria and, to a lesser extent, renal tubular proteins are widely used in the early detection of incipient nephropathy in diabetes mellitus. Recent reports have indicated detrimental effects of storage at -20 degrees C on urine proteins. This study investigated the effects of storage on the measurement of urine proteins and discusses implications for the interpretation of data.

METHODS

Two-hundred and sixty-eight specimens, collected from children with Type 1 diabetes, split into duplicate aliquots and stored at -20 degrees C and -70 degrees C, respectively, for 6-8 months, were analysed for albumin, retinol binding protein, N-acetyl glucosaminidase and creatinine, in the same assays to eliminate inter-assay variability. Two independent non-diabetic cohorts of children provided urine specimens, which were stored at -20 degrees C for one cohort and -70 degrees C for the other, to determine normal ranges for urine proteins.

RESULTS

Storage at -20 degrees C led to a variable underestimation of all three urine proteins in 20% of specimens. Creatinine was unaffected. This underestimation was greater in more concentrated urine (r2 = 0.38, P < 0.001, n = 262). Consequently storage at -20 degrees C increased the variance of the albumin/ creatinine ratio more than the variance of albumin concentration. Temperature of storage affected the normal range, which was 0.1-2.1 mg/mmol at -20 degrees C compared to 0.3-3.1 mg/mmol at -70 degrees C. The prevalence of microalbuminuria (> 2SD above the geometric mean in non-diabetic specimens stored at -20 degrees C) was 27% after storage at -70 degrees C vs. 24% after -20 degrees C. The prevalence of microalbuminuria (>2SD above the geometric mean in nondiabetic specimens stored at -70 degrees C) was 21% after storage at -70 degrees C vs. 17% after -20 degrees C.

CONCLUSIONS

Urine proteins are significantly but variably underestimated after storage at -20 degrees C. These effects account for increased variance and differences in the normal range, but have less effect on the detection of microalbuminuria than might be predicted.

摘要

目的

微量白蛋白尿以及程度较轻的肾小管蛋白，被广泛用于糖尿病早期肾病的检测。最近的报告表明，在-20℃储存对尿蛋白有不利影响。本研究调查了储存对尿蛋白测量的影响，并讨论了对数据解读的意义。

方法

从1型糖尿病儿童中收集268份标本，分成两份等分试样，分别在-20℃和-70℃储存6 - 8个月，对白蛋白、视黄醇结合蛋白、N - 乙酰氨基葡萄糖苷酶和肌酐进行分析，采用相同检测方法以消除检测间的变异性。两组独立的非糖尿病儿童队列提供尿标本，一组储存在-20℃，另一组储存在-70℃，以确定尿蛋白的正常范围。

结果

在-20℃储存导致20%的标本中所有三种尿蛋白出现不同程度的低估。肌酐不受影响。在浓度较高的尿液中这种低估更明显（r2 = 0.38，P < 0.001，n = 262）。因此，在-20℃储存使白蛋白/肌酐比值的方差增加幅度大于白蛋白浓度的方差。储存温度影响正常范围，-20℃时为0.1 - 2.1mg/mmol，而-70℃时为0.3 - 3.1mg/mmol。在-70℃储存后微量白蛋白尿的患病率（高于储存在-20℃的非糖尿病标本几何平均数2个标准差以上）为27%，而在-20℃储存后为24%。在-70℃储存后微量白蛋白尿的患病率（高于储存在-70℃的非糖尿病标本几何平均数2个标准差以上）为21%，而在-20℃储存后为17%。