Hepatitis B virus DNA stability in plasma samples under short-term storage at 42°C

We evaluated the stability of hepatitis B virus (HBV) DNA in plasma samples stored at 42°C for external quality assessment (EQA) panels of viral load. To assess the stability of plasma samples containing different concentrations of HBV DNA, serial dilutions of HBV-infected samples with a viral load of 6.40 log(10) IU/mL were made to yield viral loads of 5, 4, and 3 log(10) IU/mL. These were incubated at 42°C for up to 7 days and then frozen at -70°C. Viral load testing for HBV DNA was performed for all samples using COBAS¯ AmpliPrep/COBAS¯ TaqMan¯ HBV Test (v.2.0, Roche, Switzerland). Results were compared with fresh frozen plasma samples as a benchmark to establish acceptable measurements on the days following sample collection. Although the results of this study demonstrated a decrease in HBV DNA viral load ranging from 0.005 to 0.30 log(10) IU/mL after storage at 42°C for up to 7 days, these values did not exceed 0.5 log(10), which is the estimated intra-assay variation for molecular tests. Thus, the insignificant decrease in viral load suggests that shipment of HBV in plasma samples at temperatures of up to 42°C is permissible if they are frozen within 7 days.本研究针对病毒载量型室间质评（external quality assessment, EQA）样本，评估了42℃储存条件下血浆样本中乙型肝炎病毒（hepatitis B virus, HBV）DNA的稳定性。为探究不同HBV DNA载量血浆样本的稳定性，我们将病毒载量为6.40 log₁₀ IU/mL的HBV感染样本进行系列稀释，制备得到病毒载量分别为5、4及3 log₁₀ IU/mL的样本。将上述样本置于42℃孵育至多7天后，再置于-70℃冻存。所有样本均采用罗氏COBAS® AmpliPrep/COBAS® TaqMan® HBV核酸检测试剂盒（v2.0，瑞士罗氏）进行HBV DNA病毒载量检测。以新鲜冰冻血浆样本作为基准对照，对比样本采集后不同天数的检测结果，以确立可接受的检测结果判定标准。尽管本研究结果显示，42℃储存至多7天后，HBV DNA病毒载量出现了0.005~0.30 log₁₀ IU/mL的下降，但该降幅未超过0.5 log₁₀ IU/mL——这一数值为分子检测的批内变异估计值。因此，病毒载量的降幅无统计学意义，这表明若血浆样本可在7天内完成冻存，42℃条件下运输HBV感染血浆样本是可行的。