Stability, integrity, and recovery rate of cellular nucleic acids preserved in a new liquid-based cytology medium.

Abstract

Liquid-based cytology (LBC) has replaced the conventional Papanicolaou test in cervical cancer screening. The cervical swab specimens collected in LBC media can also be used for additional analyses including high-risk HPV (HR-HPV) test, DNA methylation analysis, and HPV E6/E7 mRNA test. The stability, integrity, and recovery rate of cellular DNA and RNA after storage at different conditions were evaluated by a quantitative real-time PCR (qPCR) based HR-HPV test, reverse transcription qPCR (RT-qPCR), and agarose gel electrophoresis. Cervical swab specimens collected in a newly developed LBC medium, VersaMedium, and ThinPrep PreservCyt medium were processed on Hologic ThinPrep 5000 instrument. Cervical exfoliative cells fixed by VersaMedium exhibited good cellular morphology with intact membranes and delineated chromatin structures. Cellular DNA preserved in VersaMedium exhibited high level of stability at both room temperature and 4°C, and remained mostly intact at 4°C for up to 28 days. Cellular RNA preserved in VersaMedium maintained higher level of stability and integrity at 4°C than at room temperature. VersaMedium also showed no apparent adverse effect on the recovery rate of nucleic acids. In addition to maintaining cellular morphology, when stored at 4°C, VersaMedium preserves cellular nucleic acids and PreservCyt medium without noticeable adverse effects on the recovery rate during purification. Therefore, VersaMedium is an appropriate LBC medium for the collection and preservation of cervical swab specimens. And VersaMedium preserved cellular nucleic acids are of such high quality that they are suitable for HR-HPV qPCR test and RT-qPCR analyses.