Effect of fixation time and freeze-thaw cycles on the molecular analysis of viral DNA.

This study was done to determine the effect of fixation time and freeze-thaw (FT) cycles on the quantitation and positivity of viral DNA. There were significant decreases in the viral DNA copies in the specimens subjected to formalin fixation more than 24 hours. However, The viral DNAs of specimens with FT cycles were not remarkably decreased as compare with those of fresh samples. These results implicate that there may be need to fix the samples less than 24 hours. Also, results of retrospective studies performed on specimens subjected to long-term fixation may be compromised.