Our long-term goal is to develop sensitive, specific, and inexpensive approaches to cervical cancer screening. In our previous proposal, we performed the first U.S.-based study of the accuracy and cost effectiveness of primary screening by traditional Pap and cervical HPV DNA testing. We found that testing for HPV was considerably more sensitive but less specific than Pap testing for detection of cervical intraepithelial neoplasia grade 3 (CIN3). While the role of high sensitivity in detecting disease cannot be disputed, when the trade-offs low specificity there are substantial cost implications, especially for a screening test that is repeated at regular intervals. Preliminary results from our group suggest that testing for the cyclin-dependant kinase inhibitor, p16INK4a, may provide a more accurate indication of disease status than either Pap or HPV DNA testing. Since p16INK4a is protein, there is potential for developing a low cost ELISA assay. Furthermore, our pilot data suggest that p16INK4a is associated with infection by variants of HPV16 that are most strongly linked with CIN3 and cancer. In HPV-associated tumors, levels of p16INK4a increase due to inactivation of Rb by HPV E7. Lastly, our preliminary data suggest that a self-collected vaginal swab for HPV DNA testing may be a viable screening option for women who avoid, or who do not have access to, pelvic examinations. In the proposed project, we plan to define the accuracy and relative cost-effectiveness of p16INK4a testing of a clinician collected sample and HPV DNA testing of a self-collected vaginal swab sample. In addition, we will explore the hypothesis that variation in levels of E7 gene expression defines differences in the oncogenic potential of HPV16 variants. While Pap test screening of healthy women has substantially reduced cervical cancer deaths over the last 50 years, false negative and false positive screening test results have also deprived women of their sense of well-being, initiated potentially harmful diagnostic testing and treatment, and wasted health-care resources. Clear public health benefits will accrue from development of more accurate and less costly screening tests.
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