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Liquid based cytology (LBC) is a method of preparing cervical cells for examination in a laboratory following a Pap smear. A Pap smear is a gynecological screening test primarily used to detect cancerous cells in the cervix, but it can also detect infections and other abnormalities. LBC is a newer way to examine the specimen collected from a Pap smear that is expected to be more sensitive and therefore better, however, some studies show that with its heightened sensitivity comes an increased number of false positives.
Traditional Pap smears are conducted by physicians who use a spatula to collect cervical cells for analysis. A small sample of cells is lightly scraped from the cervix, placed on a microscope slide, and sent to a laboratory for staining and analysis by a cytologist. Unlike a traditional Pap smear, where the cells are placed directly on a microscope slide, in liquid based cytology the head of the spatula is detached and placed into a vial containing a preservative fluid. Most liquid preservatives for liquid based cytology are ethanol-based.
The vial is then sent to the laboratory where the fluid is centrifuged to separate the cervical cells from the preservative and other materials collected by the spatula. A small sample of cervical cells is collected from the centrifuge and applied to a slide. The slide can then be stained and examined in the same manner as a traditional Pap smear by a cytologist.
Liquid based cytology has become increasingly more common in hospitals and clinics since the 1990s. The centrifuging process allows for clearer, more uniform samples that are easier for cytologists to analyze. This has also helped to reduce the number of unreadable or inconclusive tests, requiring fewer women to return to clinics for repeat testing. Liquid samples are also more suitable for human papillomavirus (HPV) testing.
Some studies also indicate that liquid based cytology increases the sensitivity and specificity of cytological reports, making the Pap smears more effective in detecting cancers and other diseases. Other studies claim that liquid based cytology is not more effective than traditional Pap smears. Despite the debate amongst physicians, liquid based cytology remains commonplace in many clinical laboratories.