Abstract

Objectives

The body of literature varies significantly regarding serum and urine osmolality stability. Therefore, our aim was to investigate the stability of serum and urine osmolality at different temperatures (room temperature (RT) 4–8 °C, −20 °C) and time conditions (8 h, 24 h, 1 month).

Methods

The stability study was conducted following the CRESS guidelines, including 40 serum and urine samples. Samples were aliquoted into three aliquots and stored as follows: primary tube stored at RT for 8 h; two capped aliquots stored at 4–8 °C for 8 h and 24 h; one aliquot stored at −20 °C for 1 month. To minimize imprecision error, serum and urine osmolality were measured by the freezing point depression method in triplicate on OSMOMAT 3000 (Gonotech, Germany) analyzer. Percentage difference (PD%) against baseline measurement was calculated. Deviations were assessed against a reference change value of 5.0%.

Results

The PD% for serum and urine osmolality was below 2.0% for all time/temperature conditions. For serum samples: primary tube after 8 h at RT PD% (95% CI) = 0.0% (−0.3, 0.2%); 8 h at 4–8 °C PD% (95% CI) = −0.4% (−0.7, 0.0%); 24 h at 4–8 °C PD% (95% CI) = −0.7% (−0.7, −0.6%); 1 month at −20 °C PD% (95% CI) = −2.1% (−2.4, −1.5%). For urine samples: after 8 h at RT PD% (95% CI) =0.6% (0.2, 0.9%); 8 h at 4–8 °C PD% (95% CI) = −0.2% (−0.5, 0.1%); 24 h at 4–8 °C PD% (95% CI) = −0.2% (−0.5, 0.0%); 1 month at −20 °C PD% (95% CI) = −2.0% (−3.0, −1.0%).

Conclusions

Changes in osmolality for tested conditions for serum and urine samples, were within acceptance criteria. Reflex and add-on osmolality testing can be performed within the same day in samples kept at RT for 8 h in primary tube and within 24 h, in aliquoted refrigerated samples, without compromising the reliability of test results. For longer storage, samples should be kept at −20 °C.

中文翻译：

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血清和尿液渗透压：8 小时、24 小时和 1 个月的样品稳定性

摘要

目标

关于血清和尿液渗透压稳定性的文献有很大差异。因此，我们的目的是研究不同温度（室温（RT）4-8°C，-20°C）和时间条件（8小时，24小时，1个月）下血清和尿液渗透压的稳定性。

方法

稳定性研究是按照 CRESS 指南进行的，包括 40 个血清和尿液样本。将样品分成三等份并按如下方式储存： 原管在室温下储存 8 小时；两个加盖的等分试样在 4-8 °C 下储存 8 小时和 24 小时；一份在 -20 °C 下储存 1 个月。为了最大限度地减少不精确误差，在 OSMOMAT 3000（Gonotech，德国）分析仪上通过冰点降低方法测量血清和尿液渗透压，一式三份。计算相对于基线测量的百分比差异 (PD%)。根据 5.0% 的参考变化值评估偏差。

结果

在所有时间/温度条件下，血清和尿液渗透压的 PD% 均低于 2.0%。对于血清样本：在 RT PD% (95% CI) = 0.0% (-0.3, 0.2%) 时 8 小时后的初级管；4–8 °C 时 8 小时 PD% (95% CI) = -0.4% (-0.7, 0.0%)；在 4–8 °C 下 24 小时 PD% (95% CI) = -0.7% (-0.7, -0.6%)；-20 °C 下 1 个月 PD% (95% CI) = -2.1% (-2.4, -1.5%)。对于尿样：RT PD% (95% CI) = 0.6% (0.2, 0.9%) 时 8 小时后；4–8 °C 下 8 小时 PD% (95% CI) = -0.2% (-0.5, 0.1%)；4–8 °C 下 24 小时 PD% (95% CI) = -0.2% (-0.5, 0.0%)；-20 °C 下 1 个月 PD% (95% CI) = -2.0% (-3.0, -1.0%)。

结论

对于血清和尿液样本的测试条件，渗透压的变化在可接受的标准范围内。反射和附加渗透压测试可以在同一天内对在原管中保存在 RT 8 小时的样品和在 24 小时内，在等分的冷藏样品中进行，而不会影响测试结果的可靠性。如需更长的储存时间，样品应保存在 -20 °C。