Rapid removal of cytology slide coverslips for DNA and RNA isolation

Because of consistent demand for identification of molecular targets for diagnosis and treatment, ancillary tests are increasingly being developed for cytology specimens. One time-consuming step in this procedure is glass coverslip removal by xylene. Here we describe a method for rapid coverslip removal using liquid nitrogen.

Direct smears were prepared from residual pleural fluid, Diff-Quik stained, then covered with a glass coverslip. Coverslips were then removed by either immersing the slides in xylene for 3 to 4 days, or by a razor blade after rapidly freezing the slides in liquid nitrogen. The DNA or RNA was extracted, and the quantities of DNA and RNA were evaluated. The amplifiability of the DNA and RNA was also evaluated by real-time polymerase chain reaction (PCR) and real time reverse transcription (RT)-PCR.

The concentrations of DNA isolated using the two procedures are not significantly different (2.79 μg/mL with liquid nitrogen method versus 2.56 μg/mL with xylene method, n = 5). Similar results were observed for RNA concentration (13.28 μg/mL versus 12.22 μg/mL). The DNA extracted from the two procedures can be amplified without significant difference. Similar results were obtained from real time RT-PCR for RNA samples.

By removing the coverslip from the cytology slides using the liquid nitrogen method, DNA and RNA can be extracted from the slides without affecting the quantity and quality of the nucleic acids, and is equivalent to the xylene coverslip removal method.