In the SurePath method, the sample is vortexed, strained, layered onto a density gradient, and centrifuged. Instruments required are a computer-controlled robotic pipette and a centrifuge. The cells form a circle 12.5 mm in diameter. The ThinPrep method requires an instrument and special polycarbonate filters. After the instrument immerses the filter into the vial, the filter is rotated to homogenize the sample. Cells are collected on the surface of the filter when a vacuum is applied. The filter is then pressed against a slide to transfer the cells into a 20 mm diameter circle. Both methods result in a well-preserved approximate monolayer of cells with a background devoid of blood and mucus. However, the current high cost of these patented commercial systems, requiring cytotechnologists and pathologists to interpret the ThinPrep slides, has led to the development and evaluation of less costly alternatives. One such method referred to as SpinThin, developed by Khalbuss et al. (2000), uses a modified electric toothbrush to release the cells into suspension from the collecting device. The cells are spun directly onto a 10 × 20 mm area of a glass slide using a Cytospin II cytocentrifuge with megafunnel. Results correlated well with conventional smears and follow-up histology. Another method described by Johnson et al. (2000) places the cervical collection device into 15 ml of CytoRich Red (TriPath Imaging), a proprietary formula of buffering agents, emulsifiers, formaldehyde, and alcohol. After arrival in the laboratory, cell suspensions are vortexed, poured through tulle and centrifuged. Following centrifugation, the supernatant is discarded and the sediment is vortexed. A drop of sediment is placed into an 8 ml Hettich cytocentrifuge chamber prefilled with 2 ml of CytoRich Yellow (TriPath Imaging), a proprietary Saccomanno-like fixative that prevents dehydration and collapse of 3-dimensional structures when slides are air-dried, and then spun onto adhesive-coated slides. Advantages include batch processing and reusability of its funnel assembly, which decreases the bulk of disposable plastic that can significantly impact the environment as well as add to the cost of individual tests.
Liquid-based cytology
Papanicolaou stain
Cytopathology
Hematopathology
Liquid biopsy
Frozen section procedure
Microstaging
Trichology