HPV Testing Bests Pap for Cervical Screening

Primary human papillomavirus (HPV) testing may be more effective than Pap testing at screening for cervical cancer: In the HPV FOCAL study, HPV testing detected precancerous cervical lesions earlier, and an initial negative HPV test meant women were less likely to have lesions 4 years later.

HPV is the most common sexually transmitted infection in the United States, affecting 79 million people. Although many cases clear up on their own, certain strains—notably HPV 16 and 18—are responsible for virtually all instances of cervical cancer. However, the cancer can be prevented by detecting and removing precancerous lesions.

A Pap test reveals morphologic changes in cervical cells that could indicate precancerous changes, whereas HPV testing detects an HPV virus based on the presence of the virus's genetic material in cervical cells. In both cases, a follow-up colposcopy is needed to identify precancerous lesions.

Currently, the U.S. Preventive Services Task Force (USPSTF) recommends cervical cancer screening with a Pap test every 3 years for women ages 21 to 65, or, for women ages 30 to 65, combination Pap and HPV testing every 5 years.

To compare the effectiveness of the two techniques, Gina Ogilvie, MD, of the University of British Columbia in Vancouver, Canada, and her team assigned 19,009 healthy women ages 25 to 65 to receive HPV or Pap testing. Those with a negative HPV test were retested 4 years later with HPV and Pap screening, whereas those with a negative Pap test were retested with a Pap 2 years later, followed by combination testing 2 years after that. Those with a positive HPV or Pap test at any point had additional testing to decide whether a colposcopy was needed.

In previously published results from the HPV FOCAL study, significantly more women who underwent initial HPV testing had precancerous changes known as high-grade cervical intraepithelial neoplasia grade 2 or worse (CIN2+) than women who had Pap testing (16.5 women/1,000 vs. 10.1/1,000, respectively). Now, new data from HPV FOCAL show that 4 years later, fewer women with an initial negative HPV test had CIN2+ lesions compared with women who started with a negative Pap test (3.6 women/1,000 vs. 10/1,000, respectively).

“At the end of the day, the HPV test was better at detecting precancerous lesions earlier, and a negative HPV test offers you more assurance that you're not going to have a precancerous lesion 4 years later,” Ogilvie says. She hopes the study will inform the work of agencies such as the USPSTF, which is expected to release new screening guidelines later this year.

For Krishnansu Tewari, MD, of the University of California, Irvine, in Orange, who was not involved in the study, the research provides clear evidence in support of HPV testing. However, he points out that because the study was done in Canada, it may not be representative of the U.S. population. In addition, the study excluded women diagnosed with CIN2+ lesions within the past 5 years.

To understand the utility of the test in the United States, “I think the study needs to be redone in the U.S. in women that are at higher risk of cervical cancer, particularly those with a history of high-risk HPV infection and/or CIN,” he says.

Warner Huh, MD, of The University of Alabama at Birmingham, who was also not linked to the study, notes that because disease and HPV rates will drop with HPV vaccination, there is a need for a more sensitive screening test such as HPV testing. “The overall impact of the Pap smear cannot be overstated; however, going forward, its effectiveness as a screening test will be limited,” he says. –Catherine Caruso