血清标本的冷冻保存对胰岛素稳定性的影响

Effects of cryopreservation on the stability of serum insulin

目的分别探讨低温(-20℃和-80℃)以及冻存时间对血清胰岛素(INS)稳定性的影响。方法分离胶真空采血管采集72份静脉血并分离血清,于-20℃及-80℃分别放置3、7、14d,使用微粒子化学发光免疫分析法测定其INS水平,并按INS水平分为低、中和高3组。除使用Bland-Altman分析法评估两种温度条件间,以及各时间点间INS水平的可比性,还将两个时间点INS水平差异率与INS的总变化极限(TCL)值进行比较,以进一步评估偏差的可接受性。结果在-20℃和-80℃条件下储存相同时间的标本,其INS水平具有很好的可比性;冻存后第3天的标本,Bland-Altman法显示其INS与即时水平无可比性,但3d后趋于稳定;相对于即时水平,多数血清标本冻存不同时间后INS降低幅度低于TCL值(低值组TCL为13.3%,中、高值组TCL为15.6%),变化幅度基本可被接受。结论 -20℃和-80℃保存血清标本,对防止INS被降解的效果相当;即使低温保存,血清INS也存在一定程度的降解,但如无法及时检测,低温保存仍为防止INS被降解的有效方法。

Objective To investigate the effect of cryopreservation on the stability of serum insulin.Methods An overall 72 venous blood specimen were collected with separator gel tubes and serum samples were subsequently separated,then kept in freezer at-20 ℃ and-80 ℃,respectively,for 0,3,7 and 14 days until insulin level assayed by a microparticle chemiluminescence immunoassay based system.The comparability of insulin level between-20 ℃ and-80 ℃,or between different time points,was implemented by Bland-Altman analysis.The acceptability of the difference between serum insulin levels of two time points,was further evaluated by comparing their difference ratio with total change limit（TCL）value of insulin level.Results For serum samples stored at-20 ℃ and-80 ℃freezer for the same period of time,comparable insulin level was observed.Incomparable insulin level was observed from the 3 rd day of storage,in comparison with that of the 0 th day,and after 3 days′cryopreservation,serum insulin level tended to be stable again.For most samples,the difference ratio of insulin level between a certain time point and that of the 0 th day,was less than TCL values（for low insulin level group：15.6%;for medium or high insulin level group：13.3%）,which could be theoretically accepted.Conclusion The storage of serum samples at-20 ℃is as effective as at-80 ℃ on preventing the decomposition of insulin;Even cryopreserved,serum insulin would still undergo certain amount of decomposition.If it could not be timely assayed,long-term cryopreservation of serum samples is still recommended.