Several studies have investigated the effect of repeated freeze–thaw (F/T) cycles on RNA detection for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). However, no data are available regarding the effect of repeated F/T cycles on SARS-CoV-2 antibody detection in serum. We investigated the effect of multiple F/T cycles on anti-SARS-CoV-2 IgG detection using an ELISA test targeting the nucleocapsid antibodies. Ten positive and 1 negative SARS-CoV-2 IgG sera from 11 participants, in replicates of 5, were subjected to a total of 16 F/T cycles and stored at 4 °C until tested by ELISA. Statistical analysis was performed to test for F/T cycle effect. None of the 10 positive sera became negative after 16 F/T cycles. There was no significant difference in the OD average reading between the first and last F/T cycles, except for one serum with a minimal decline in the OD. The random effect linear regression of log (OD) on the number of cycles showed no significant trend, with a slope consistent with zero (B=−0.0001; 95 % CI −0.0008; 0.0006; P-value=0.781). These results suggest that multiple F/T cycles had no effect on the ability of the ELISA assay to detect SARS-CoV-2 IgG antibodies.

中文翻译：

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多次冻融循环对抗 SARS-CoV-2 IgG 抗体检测的影响

多项研究调查了重复冻融 (F/T) 循环对严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) RNA 检测的影响。然而，没有关于重复 F/T 循环对血清中 SARS-CoV-2 抗体检测影响的数据。我们使用针对核衣壳抗体的 ELISA 测试研究了多个 F/T 循环对抗 SARS-CoV-2 IgG 检测的影响。来自 11 名参与者的 10 份阳性和 1 份阴性 SARS-CoV-2 IgG 血清，重复 5 次，共进行 16 次 F/T 循环并储存在 4°C 下，直到通过 ELISA 进行测试。进行统计分析以检验 F/T 循环效应。16 次 F/T 循环后，10 份阳性血清均未转为阴性。第一个和最后一个 F/T 循环之间的 OD 平均读数没有显着差异，除了一种 OD 下降最小的血清。log (OD) 对循环数的随机效应线性回归显示没有显着趋势，斜率与零一致（B=-0.0001；95% CI -0.0008；0.0006；P值=0.781）。这些结果表明，多个 F/T 循环对 ELISA 检测 SARS-CoV-2 IgG 抗体的能力没有影响。