Sgoutas D S, Tuten T
Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322.
Clin Chem. 1992 Sep;38(9):1873-7.
We studied the effect of freezing and thawing of serum on the determination of lipoprotein(a) [Lp(a)] with a commercial enzyme-linked immunosorbent assay (ELISA) and an immunoturbidimetric assay (ITA). Portions of sera from 11 apparently healthy persons and pooled sera, from an additional 10 subjects were frozen at either -20 or -70 degrees C and thawed at room temperature. Cycles of freezing and thawing were repeated during the experiments (1 month). Samples were assayed for Lp(a) after thawing. Pooled sera were subjected to quick freezing at -70 degrees C and thawing at room temperature in cycles. Results show a significant (P less than 0.05) decrease in Lp(a) concentration in sera subjected to freezing and thawing. Samples thawed from -20 degrees C gave concentrations by ELISA that were significantly lower than those of fresh samples after one freeze-thaw cycle. By ITA the decrease was significant only after two cycles. In specimens frozen at -70 degrees C, Lp(a) concentrations determined by ELISA decreased after two cycles, and by ITA after three freeze-thaw cycles. Serum samples subjected to quick freezing at -70 degrees C and thawing did not show significant decreases in Lp(a) immunoreactivity during four cycles. Immunoreactivity of Lp(a) in samples stored at 4 degrees C decreased after 6 days but fell faster in serum samples subjected to freezing and thawing before storage at 4 degrees C.
我们使用商业酶联免疫吸附测定法（ELISA）和免疫比浊法（ITA）研究了血清冻融对脂蛋白(a) [Lp(a)]测定的影响。从11名表面健康的个体采集的部分血清以及另外10名受试者的混合血清，分别在-20℃或-70℃冷冻，并在室温下解冻。在实验期间（1个月）重复冻融循环。解冻后对样本进行Lp(a)测定。混合血清在-70℃快速冷冻并在室温下循环解冻。结果显示，经历冻融的血清中Lp(a)浓度显著降低（P<0.05）。从-20℃解冻的样本，经过一个冻融循环后，ELISA测定的浓度显著低于新鲜样本。通过ITA法，仅在两个循环后降低才显著。在-70℃冷冻的样本中，ELISA法测定的Lp(a)浓度在两个循环后降低，而ITA法在三个冻融循环后降低。在-70℃快速冷冻和解冻的血清样本在四个循环中Lp(a)免疫反应性未显示出显著降低。储存在4℃的样本中Lp(a)的免疫反应性在6天后降低，但在储存在4℃之前经历冻融的血清样本中下降得更快。
