Trials That Matter: Liquid-Based Cervical Cytology: Disadvantages Seem to Outweigh Advantages

Liquid-based cytology is a technique for preserving and preparing cells for cytologic study. As applied to cervical cytology, cells are obtained by scraping the external cervix uteri with a spatula and by rotating a cytobrush in the endocervix. Instead of being spread onto a glass slide and fixed, the samples are suspended in a vial of liquid preservative. In the laboratory, processing removes debris and places a thin layer of cells onto slides that are stained and read similarly to conventional cytology. Systematic reviews have concluded that the quality of the evidence about liquid-based cytology has not been good enough to judge its performance relative to conventional cytology (1, 2). The lack of large randomized studies comparing the 2 techniques is an important evidence gap (1, 3). In 2003, the U.S. Preventive Services Task Force (USPSTF) found the evidence insufficient to make a recommendation about using liquid-based cytology (4).