Previous studies have shown that certain types of HPV cause most cervical cancers, raising the possibility that testing for these HPV types may be one way to screen for the disease. However, there has been uncertainty about how reliable and accurate HPV testing would be.

The purpose of this study was to provide data on how HPV testing would perform as a screening tool in a population at high risk for cervical cancer. The research team, including investigators from the United States and Costa Rica, evaluated HPV testing in a randomly selected group of 8,554 women in Guanacaste Province, Costa Rica, where cervical cancer rates are high. The HPV tests used were the Hybrid Capture Tube test and its successor, Hybrid Capture II,² which detect HPV DNA. Women in the study were also screened using other methods, including the conventional Pap test.

The Hybrid Capture II test accurately detected a high proportion of the precancerous, high-grade lesions as well as all cases of cervical cancer in this population. Using an HPV level of 1 pg/ml (1 picogram of HPV DNA per milliliter of solution) as cutpoint — any test result of one or above was considered HPV positive — the researchers found that the test detected 88.4 percent of the precancerous lesions and 100 percent of the cancers. At the 1 pg/ml cutpoint, the test was 89 percent specific - that is, 89 percent of the women without high-grade lesions or cancer were accurately classified as negative.

At cutpoints above 1 pg/ml, HPV testing was less sensitive — it did not detect as many of the high-grade lesions. At lower cutpoints it was sensitive but not specific in this group of women — it identified as positive many women without high-grade lesions.

The investigators conclude that the cutpoint of 1.0 yielded an optimal trade-off between high sensitivity and reasonable specificity in this population. Compared to conventional Pap testing, in which cervical cells are examined with a microscope, the HPV test was more sensitive but less specific.

The authors also conclude that HPV testing can be a useful screening tool. "Our findings suggest that HPV testing is a viable technology worthy of consideration in cervical cancer prevention programs," said Mark Schiffman, M.D., an epidemiologist at the NCI and the study's principal investigator.

However, the authors also caution that the usefulness of HPV testing will vary according to the population being screened and other factors, such as prevalence of other screening methods and cost. "Decisions on optimal methods of screening will probably have to be made on a regional or national basis and depend on health economic analyses," Schiffman said.

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2. Digene Corporation, Gaithersburg, Md.