The Role of Human Papilloma Virus Testing in Cervical Cancer Prevention

Molly C. Fey, FNP, MSN; Margaret W. Beal, CNM, PhD

Disclosures

J Midwifery Womens Health. 2004;49(1) 

In This Article

Pap Test Technology

Two new technologies have been developed to improve conventional Pap test techniques. Thin-layer, liquid-based cytology was first approved by the Food and Drug Administration (FDA) for commercial use in 1996. With this method, a cervical sample is collected by cytobrush and suspended in a cell-preserving solution for automated slide preparation at the laboratory. The liquid is spun and passed though a microfilter and then mechanically transferred to the slide as a monolayer. The slide is then processed and interpreted as a conventional Pap slide. This filtering process allows for a greater number of cells to be placed on the slide and fewer artifacts in cellular morphology. Excess blood, mucous, and inflammatory cells are reduced, slide quality is greatly improved, and the slide is thus easier to interpret.[44] One benefit to liquid-based cytology is the option for "reflex" testing. By using residual material from the original sample submitted, testing for HPV, gonorrhea, and chlamydia can be performed following an irregular Pap result, eliminating the need for a return visit or handling of additional specimen kits.[44]

In numerous studies, liquid-based cytology resulted in significantly better sensitivity over the conventional Pap in detecting LSIL and HSIL.[44] Other investigations have found decreased specificity with liquid-based cytology, particularly in populations with higher disease prevalence. When sensitivity is gained at the expense of specificity, more patients are subject to expensive and invasive intervention. Liquid cytology is also a more costly test, and financial impact also demands further investigation.[44]

Computer-assisted automated slide interpretation is another recent technology geared toward improving screening of the Pap test. The FocalPoint slide profiler (TriPath Imaging, Inc., Burlington, North Carolina), approved for primary screening of both liquid-based (SurePath slides) and conventional slides, uses a high-speed video camera and can scan approximately 250 slides per day. The computer interprets images for irregularities and hierarchically orders slides, indicating to cytologists those that are abnormal and require human interpretation. Using this program, up to 25% of slides are deemed unlikely to contain abnormal cells and are filed without human review following computer re-screen, decreasing the manual screening load by up to 25% [personal communication TriPath Imaging, November 18, 2003].[1,2,12,46]

Recent validation studies indicated that the FocalPoint system performs equally well with both general and high-risk populations.[47] Long-term costs and benefits of utilizing liquid-base cytology and computerized screening in cervical cancer prevention have yet to be determined.

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