M Krajden1, J M Minor, J Zhao, O Rifkin, L Comanor. 1. Department of Laboratory Medicine and Pathology, The Toronto Hospital and Toronto Medical Laboratories, Ont., Canada. mel.krajden@bccdc.hnet.bc.ca
Abstract
OBJECTIVES: Quantification of hepatitis C virus (HCV) RNA in serum is used to assess the probability of treatment response and to monitor antiviral therapy. Since serum specimens often are shipped to central sites for HCV RNA testing, it is important to define conditions that preserve HCV RNA integrity. METHODS: We evaluated the stability of HCV RNA in 25 previously frozen (PF) and 11 fresh, never previously frozen (NPF) specimens subjected to handling and short-term storage conditions that mimic those encountered during interlaboratory shipping. All sera were separated within 4 h of collection. PF samples covering a approximately 3 log10 HCV RNA dynamic range were thawed, divided into aliquots, incubated at 4, 23, and 37 degrees C (+/- 1.5 degrees C) for 24, 48, 72 and 96 h (+/- 2 h), and then refrozen at -70 degrees C prior to testing with the Quantiplex HCV RNA 2.0 assay. Eleven NPF samples were stored at -70, -20, and 4 degrees C (+/- 1.5 degrees C) for up to 1 month prior to testing. RESULTS: Linear regression analysis showed no HCV RNA degradation in PF specimens kept at 4 degrees C over 4 days. However, HCV RNA levels in PF specimens decreased over 4 days by 20 and 105% at 23 and 37 degrees C, respectively. Three independent statistical methods showed that the probability of specimen failure in PF specimens, defined as a loss of 20% or more of HCV RNA, was lowest at 4 degrees C and increased with increasing temperature. The HCV RNA quantification of the 11 NPF specimens stored at 4 degrees C was similar to their frozen controls. CONCLUSION: HCV RNA in separated serum specimens is stable for at least 4 days at 4 degrees C.
OBJECTIVES: Quantification of hepatitis C virus (HCV) RNA in serum is used to assess the probability of treatment response and to monitor antiviral therapy. Since serum specimens often are shipped to central sites for HCV RNA testing, it is important to define conditions that preserve HCV RNA integrity. METHODS: We evaluated the stability of HCV RNA in 25 previously frozen (PF) and 11 fresh, never previously frozen (NPF) specimens subjected to handling and short-term storage conditions that mimic those encountered during interlaboratory shipping. All sera were separated within 4 h of collection. PF samples covering a approximately 3 log10 HCV RNA dynamic range were thawed, divided into aliquots, incubated at 4, 23, and 37 degrees C (+/- 1.5 degrees C) for 24, 48, 72 and 96 h (+/- 2 h), and then refrozen at -70 degrees C prior to testing with the Quantiplex HCV RNA 2.0 assay. Eleven NPF samples were stored at -70, -20, and 4 degrees C (+/- 1.5 degrees C) for up to 1 month prior to testing. RESULTS: Linear regression analysis showed no HCV RNA degradation in PF specimens kept at 4 degrees C over 4 days. However, HCV RNA levels in PF specimens decreased over 4 days by 20 and 105% at 23 and 37 degrees C, respectively. Three independent statistical methods showed that the probability of specimen failure in PF specimens, defined as a loss of 20% or more of HCV RNA, was lowest at 4 degrees C and increased with increasing temperature. The HCV RNA quantification of the 11 NPF specimens stored at 4 degrees C was similar to their frozen controls. CONCLUSION:HCV RNA in separated serum specimens is stable for at least 4 days at 4 degrees C.