Guidance on the use of liquid-based cytology for cervical screening

LBC is a new method of cervical cell sample preparation. Samples are collected in the usual way, but using a brush-like device rather than a spatula. The head of the device is rinsed or broken off into a vial of preservative fluid so that most or all of the cervical cells are retained. Samples are transported to the laboratory where they are mixed to disperse the cells. Cellular debris, such as blood or mucus, is removed and a thin layer of cervical cells is deposited on a microscope slide, which is then stained.

Potential advantages of the LBC method include an improved means of slide preparation, producing more homogeneous samples than the Pap smear (which may make slides easier to read), increased sensitivity and specificity, and improved efficiency of handling laboratory samples, resulting in increased laboratory productivity.

Current methods that use LBC technology include:

• SurePath (formerly AutoCytePREP or CytoRich LBC).

  • The SurePath method requires that the collection device be retained in the proprietary SurePath collection vial, which contains transport fluid, so that all cervical cells collected are sent to the laboratory. Vials are vortexed and centrifuged by laboratory personnel; all subsequent preparation of the sample and slide is automated using the Prepstain machine, which processes 48 samples at a time.

• Cytoscreen

  • Cytoscreen is a manual method of sample preparation using a proprietary sample collection device (CYTOPREP) and transport fluid (CYTeasy). Samples are vortexed and a photometric reading taken to estimate the cellularity of the sample. An aliquot of the sample is centrifuged onto a glass slide that is then stained using normal laboratory procedures.

• Labonard Easy Prep

  • Labonard Easy Prep is a manual method of sample preparation that uses a proprietary sample collection device (CYTOPREP brush) and fixative (CYTOscreen). An aliquot of sample fluid is placed in a separation chamber attached to a glass slide containing absorbent paper. Cervical cells sediment onto the slide in a thin layer and slides are stained using normal laboratory procedures.

• ThinPrep

  • ThinPrep provides a semi-automated (T2000) or fully automated (T3000) method of sample preparation. Cervical samples are rinsed with proprietary PreservCyt transport medium into a vial, which is then processed by the ThinPrep method using the T2000 or T3000 machine. The T2000 machine processes slides individually, while the T3000 machine is a fully automated device that can batch process up to 80 specimens per cycle. Subsequent staining and microscopic evaluation of the slides is conducted in a similar manner to a conventional smear test.

NICE first issued guidance on the use of LBC for cervical screening in June 2000.