Liquid-based cytology: Technical aspects

Liquid-based cytology (LBC) is a monolayer slide preparation technology that has outperformed conventional Pap smears because of improved fixation, decreased obscuring factors, and standardized cell transfer. In LBC, samples are collected by completely immersing the sampling device into the company vial containing preservative fluid, whereby the cells are preserved and fixed simultaneously unlike conventional smears where the sample is smeared onto the glass slide and fixed separately. To date, two major liquid-based preparation methods are known - ThinPrep and SurePath. These two methods are different in their principles of cell harvesting but produce similar preparations. SurePath works on the principle of density gradient sedimentation. In this, a sample is vortexed and strained to break the mucus and large cell groups and then is treated through a density gradient centrifugation process to remove blood and debris. The cell pellet is resuspended and is allowed to sediment onto a glass slide. This is followed by staining on the PrepStain instrument. Government Medical College and Hospital, Nagpur, India, uses the SurePath method which was approved by FDA in the USA in 1999. Our institution uses Rovers Cervex-Brush to collect the cells from the transformation zone. This chapter describes the principle of SurePath and the processing of cervicovaginal specimen using the fully automated system in the laboratory.