Researchers Study Methods To Improve Cervical Cancer Screening

Researchers at the Johns Hopkins School of Public Health announced today that they will study more than 7,500 Mexican women to compare the accuracy of the Hybrid Capture II test for human papilloma virus (HPV) on self-collected specimens to that of a Pap smear obtained during a pelvic examination in screening for cervical cancer. The School's work will be part of an international collaboration to improve cervical cancer screening. The international group includes the School, the Digene Corporation, and the National Institute for Public Health and the Mexican Institute for Social Security (IMSS) in Mexico.

HPV has been linked to more than 95 percent of cervical cancers. The study will examine the potential of HPV infection testing as an alternative or a supplement to the Pap smear to accurately and efficiently identify the precursor lesions of cervical cancer. Keerti Shah, DrPH, professor, Molecular Microbiology and Immunology, Johns Hopkins School of Public Health, said, "Because Pap smear testing, the long-accepted gold standard procedure for cervical cancer screening, has only a moderate sensitivity, we are focused on developing more sensitive procedures for cervical cancer screening in order to reduce equivocal and false negative diagnoses. Also, if the self-collected specimen proves to be as effective as the Pap smear in cervical cancer screening, it would be possible to reduce markedly the number of women who have to visit the clinic for follow-up. Less than 10 percent of women participating in the study are expected to be positive for HPV."

All non-pregnant women aged 20 to 65 years seeking regular cervical cancer screening at any one of the 23 health units of the IMSS in the state of Morelos, Mexico, during a four-to-five month period will be invited to participate. Previous research conducted by the NIPH has shown a low acceptance of pap smears among Mexican women.

At the recruitment visit, all participants will provide a self-administered HPV specimen (HPV-SSS) to the health provider, who will then collect a Pap smear and a cervical HPV specimen. Researchers will also collect information on each woman's demographic data and gynecological, family planning, and sexual histories.

The specimen samples will be sent to the NIPH for HPV testing by Hybrid Capture II, a procedure developed by Digene Corporation. Evidence suggests that testing for cancer-associated HPV type by this method is a more sensitive procedure for detection of high-grade squamous intra epithelial lesions (HGSIL) than regular Pap smear cytology. This laboratory method will also make it possible to estimate viral load, perhaps increasing the specificity of diagnoses. Both the self-sampled and the clinically-obtained HPV samples will be analyzed for 13 HPV types that together account for more than 95 percent of cervical cancers.

All participants will be informed of their test results and follow-up medical appointments and transportation arrangements will be made for women with abnormal Pap results or positive HPV tests. Women who have received positive results but have not returned for further medical attention will be contacted about undergoing further evaluationand treatment.

At the conclusion of the study, researchers will estimate the proportion of cases detected and evaluate sensitivity levels for each procedure -- the HPV-SSS and the Pap smear cytology study. They will also determine if incorporating viral load information increases the sensitivity or specificity of a positive HPV-SSS test and evaluate whether predictive values are improved when results of HPV-SSS and Pap smears are combined. The researchers will compare the cost of detecting a case of HGSIL by the self-collection method to that of detection by the Pap smear.