Screening involves testing a specific group of people (in this context, women) who are at risk for a given disease (in this context, cervical pre-cancer). The aim of screening is to detect and treat the people identified as having early signs of the disease, usually this is by means of inexpensive, accurate, and reliable test that can be applied widely. There are several cervical cancer screening methods that are being used around the world. They include; cervical cytology which has been in use for the past 50 years, HPV DNA testing and visual screening tests (these are newer screening tests that are being employed for cervical cancer screening).
Each of these tests has advantages and disadvantages. None of the screening test is perfect, and
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“In the conventional Pap smear, the physician collect cells from the cervix he then smears them on a microscope slide and applies a fixative. In general, the slide is sent to a laboratory for evaluation.
From studies conventional cytology report is very high with:
• sensitivity 72%
• specificity 94%” (17)
2.5.1.1.2 Liquid-based cytology (LBC) testing
This is a method based on placing the sample into a bottle containing a liquid medium that preserves the cells. “There are two types of the technique which are the Sure-Path (TriPath Imaging) and Thin-Prep (Cytyc Corp). The media are primarily ethanol-based for Sure-Path and methanol for Thin-Prep. Once placed into the vial, the sample is processed at the laboratory into a cell thin-layer, stained, and examined by light microscopy” (17). In liquid based cytology proper acquisition of samples has crucial impact in the accuracy of the test, since cells present in the sample are ones that can be evaluated.
Studies of liquid based monolayer cytology reported:
• sensitivity 61% to 66%, (although some studies report increased sensitivity from liquid-based smears)
• specificity 82% to 91%”