The Diabetes Center, Massachusetts General Hospital, and Harvard Medical School, Boston, MA 02114, USA.
Clin Chem. 2011 Feb;57(2):286-90. doi: 10.1373/clinchem.2010.150250. Epub 2010 Oct 28.
Determining the stability of stored samples for assays that were not available at the time of original collection is problematic. To assess sample stability for a relatively new assay of glycated albumin (GA), we first measured GA in fresh samples and in samples stored for 19-23 years. We then compared the regression of the contemporaneous glycohemoglobin (Hb A(1c)) values against the GA results from fresh vs stored samples, reasoning that similar slopes and intercepts would provide strong, albeit indirect, support for the stability of the stored samples for GA measurements.
We assayed 90 samples frozen for 19-23 years and 90 fresh samples from participants in the Diabetes Control and Complications trial cohort for GA. Hb A(1c) was measured contemporaneously in fresh samples at each time period. A single normal-errors linear model regressed the Hb A(1c) values on the GA, with an additional effect for collection period (fresh vs stored for GA) and the interaction of period and GA.
Analysis of the regressions lines between GA and Hb A(1c) revealed intercepts (3.69 and 2.97 for the fresh and stored samples, respectively) and slopes (0.198 vs 0.187) that were not significantly different (P = 0.182 and P = 0.639, respectively).
This simple approach can be used to assess the stability of stored samples in new assays. Samples stored for as long as 23 years are suitable for the GA assay.
对于在原始采集时不可用的分析物，确定储存样本的稳定性是有问题的。为了评估一种相对较新的糖化白蛋白（GA）分析物的样本稳定性，我们首先测量了新鲜样本和储存了 19-23 年的样本中的 GA。然后，我们比较了新鲜样本和储存样本的同时糖化血红蛋白（Hb A(1c)）值与 GA 结果之间的回归，我们推断相似的斜率和截距将为 GA 测量的储存样本的稳定性提供强有力的、尽管是间接的支持。
我们检测了 90 个冷冻储存了 19-23 年的样本和 90 个来自糖尿病控制和并发症试验队列的新鲜样本中的 GA。在每个时间段的新鲜样本中同时测量了 Hb A(1c)。采用单一线性误差模型，将 Hb A(1c)值与 GA 进行回归，同时考虑了采集时间（新鲜样本与 GA 的储存样本）的影响以及时间和 GA 的交互作用。
GA 和 Hb A(1c)之间回归线的分析显示，截距（新鲜样本和储存样本分别为 3.69 和 2.97）和斜率（0.198 与 0.187）没有显著差异（P = 0.182 和 P = 0.639，分别）。
这种简单的方法可用于评估新分析物中储存样本的稳定性。储存长达 23 年的样本适用于 GA 分析。
