School of Forensic Medicine, China Medical University, Shenyang 110122, China.
Institute of Forensic Science, Hexi Branch of Tianjin Public Security Bureau, Tianjin 300061, China.
Fa Yi Xue Za Zhi. 2021 Feb;37(1):11-14. doi: 10.12116/j.issn.1004-5619.2019.491115.
Objective To investigate the stability of IgE in postmortem plasma and hemolyzed samples under different storage conditions and freezing-thawing. Methods Thirty nine cardiac blood samples were collected from non-frozen corpses with the postmortem interval of less than 48 hours, including 20 plasma samples and 19 hemolyzed samples taken from whole blood. The samples were stored at -20 ℃, 4 ℃ and 25 ℃ for 28 d and at -80 ℃ for 1 year to evaluate the stability of IgE under different storage conditions. Repeated freezing-thawing treatment was conducted for 5 times to explore the stability of IgE in postmortem plasma and hemolyzed samples. IgE concentration in plasma and hemolyzed samples was detected by electroluminescence before and after treatment. Results The degradation rates of IgE in plasma samples under the three storage conditions, -20 ℃, 4 ℃ and 25 ℃ were close. After 28 d, the mean value was about 15%, the degradation speed of IgE in hemolyzed samples was faster than that of plasma under the same condition （<0.05） and the degradation rate was faster than other two conditions under 25 ℃ （<0.05）. The differences in the concentration of plasma samples after freezing at -80 ℃ for 1 year and that before freezing had no statistical significance （ >0.05）, while the concentration of hemolyzed samples was degraded after freezing at -80 ℃ for 1 year （<0.05）. The differences between the detection results of plasma and hemolyzed samples after repeated freezing-thawing for 5 times and that before freezing-thawing showed no statistical significance （ >0.05）. Conclusion IgE has good freezing-thawing stability in postmortem plasma and hemolyzed samples. Stability of IgE is better in postmortem plasma samples than hemolyzed samples, thus it is recommended to separate plasma from postmortem blood samples as soon as possible in forensic practice.
目的 探讨不同储存条件及冻融对死后血浆和溶血样本中 IgE 稳定性的影响。 方法 收集尸检间隔<48 h 的非冷冻尸体 39 例心血，每份标本包括 20 份血浆样本和 19 份全血溶血样本。标本分别在-20℃、4℃和 25℃下储存 28 d，-80℃储存 1 年，评估不同储存条件下 IgE 的稳定性。对血浆和溶血样本进行 5 次重复冻融处理，以探索 IgE 在死后血浆和溶血样本中的稳定性。处理前后应用电化学发光法检测血浆和溶血样本中 IgE 浓度。 结果 在-20℃、4℃和 25℃ 3 种储存条件下，血浆样本中 IgE 的降解率接近，28 d 后平均约为 15%；同一条件下，溶血样本中 IgE 的降解速度快于血浆（<0.05），且在 25℃下的降解速度快于其他两种条件（<0.05）。-80℃冻存 1 年后血浆样本的浓度与冻存前相比无统计学差异（>0.05），而-80℃冻存 1 年后溶血样本的浓度发生降解（<0.05）。重复冻融 5 次后血浆和溶血样本的检测结果与冻融前相比无统计学差异（>0.05）。 结论 死后血浆和溶血样本中 IgE 具有良好的冻融稳定性。与溶血样本相比，血浆样本中 IgE 的稳定性更好，因此建议在法医实践中尽快从死后血样中分离血浆。
