In the traditional Pap test, cell samples are obtained from the vagina, cervix, and cervical canal and spread on a glass slide. In the ThinPrep Pap test, cell samples are collected using a special brush that is immediately washed in a special fluid. The ThinPrep machine then filters out the cells from the solution and deposits them in a thin uniform monolayer (a single layer of cells) on a glass slide.
The ThinPrep Pap method has some significant advantages. It removes contaminants such as blood and mucus which frequently obscure cells in the traditional Pap smear. The monolayer of cells is also easier to examine under the microscope. This results in an increased rate of detection of abnormal cells. The disadvantage is the increased cost incurred by the collection fluid and cost of continued operation of the machine.