Krajden M, Minor J M, Rifkin O, Comanor L
Department of Laboratory Medicine and Pathology, The Toronto Hospital and Toronto Medical Laboratories, Toronto, Canada.
J Clin Microbiol. 1999 Jun;37(6):1683-6. doi: 10.1128/JCM.37.6.1683-1686.1999.
Quantification of hepatitis B virus (HBV) DNA and hepatitis C virus (HCV) RNA often is performed in specimens that have been frozen and thawed more than once. To ensure optimal therapeutic and prognostic value, it is important to establish whether viral load measurements are affected by repeated freeze-thaw (FT) cycles. We therefore evaluated the effect of multiple FT cycles on HBV DNA and HCV RNA quantification by testing serum specimens subjected to one (baseline), two, four, and eight FT cycles with the appropriate Chiron Quantiplex assay. Linear regression analysis showed minor increases of 1.7% per FT cycle for both HBV DNA and HCV RNA. The rise in HCV RNA levels was more pronounced among low-concentration samples, since further analysis revealed an increase of 3.2% per FT cycle among samples with 0.2 to 3.86 Meq of HCV RNA per ml. Given that the coefficient of variation for the Quantiplex assays is generally 10 to 15%, the minor increases in HBV DNA and HCV RNA levels with progressive FT cycles for the specimens tested were recognized only because analysis of variance revealed a statistically significant trend (P < 0.05). Due to the minor statistical trend, the clinical impact for individual patient specimens is likely to be limited, but it may deserve further study. In conclusion, the concentration of HBV DNA and HCV RNA in serum specimens subjected to up to eight short-term FT cycles was stable.
乙型肝炎病毒（HBV）DNA和丙型肝炎病毒（HCV）RNA的定量检测通常在经过多次冻融的标本中进行。为确保最佳的治疗和预后价值，确定病毒载量测量是否受反复冻融（FT）循环的影响非常重要。因此，我们通过使用适当的Chiron Quantiplex检测法检测经过1次（基线）、2次、4次和8次FT循环的血清标本，评估了多次FT循环对HBV DNA和HCV RNA定量的影响。线性回归分析显示，HBV DNA和HCV RNA每FT循环均有1.7%的轻微增加。HCV RNA水平的升高在低浓度样本中更为明显，因为进一步分析显示，每毫升含有0.2至3.86 Meq HCV RNA的样本中，每FT循环增加3.2%。鉴于Quantiplex检测法的变异系数通常为10%至15%，所检测标本的HBV DNA和HCV RNA水平随FT循环次数增加而出现的轻微升高只是因为方差分析显示有统计学显著趋势（P<0.05）才被识别出来。由于这种轻微的统计学趋势，对个体患者标本来说临床影响可能有限，但可能值得进一步研究。总之，经过多达8次短期FT循环的血清标本中HBV DNA和HCV RNA的浓度是稳定的。
