Effects of Formalin Fixation and Prolonged Block Storage on Detection of Hepatitis C Virus RNA in Liver Tissue

摘要

It has been suggested that prolonged formalin fixation and block storage adversely affect hepatitis C virus (HCV) ribonucleic acid (RNA) detection in tissue by reverse transcriptasepolymerase chain reaction (RT-PCR). We attempted to determine whether short-term perfusion fixation (3ndash;5 days) or prolonged formalin storage adversely affects the detection of HCV RNA in paraffin-embedded tissue in comparison with 24-h fixation. Also, we examined the effects of prolonged storage of paraffin blocks on the sensitivity for HCV detection. We performed RT-PCR in formalin-fixed explanted livers from 20 liver allograft recipients known to be HCV positive (10 with specimens stored for 2ndash;4 years and 10 with specimens stored for 4 years). We compared the results of perioperative needle liver biopsy specimens fixed overnight with liver sections fixed by perfusion for 3ndash;5 days and bulk liver tissue stored in formalin for years (mean, 6.25 years; range, 2ndash;11 years). HCV RNA was detected in 100percnt;, 85percnt;, and 0percnt; of specimens fixed for 24 h, 3ndash;4 days, and years, respectively. We conclude that HCV can be readily detected in tissue fixed by formalin overnight, sensitivity decreases slightly with intermediate-length fixation, and HCV is rendered undetectable by prolonged fixation. In addition, retention of formalin-fixed tissue in paraffin blocks does not affect the sensitivity of HCV detection.