Study: HPV Tests Better at Predicting Cervical Cancer Than Pap Tests
No Significant Gain From Combining the Tests, Study Shows
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Comparing HPV to Pap Tests for Cancer Screening
The study recruited more than 47,000 women aged 25 and older from 61 clinical trial sites in 23 states.
Women were included in the study if they weren’t pregnant and hadn’t been diagnosed with low-grade cervical cell abnormalities within the last year.
All women had two swabs of cells taken from their cervix. The samples were tested for HPV viruses and the appearance of the cells was examined under a microscope.
All women who tested positive for HPV, those who had abnormal Pap smear results, and a random sample of those who had normal test results were sent to have a colposcopy, a closer examination of the cervix.
Overall, the prevalence of advanced cervical lesions among women in the study, which are considered to be precursors to cancer, was less than 2%.
Of the women diagnosed with the most advanced precancers, 92% tested positive for HPV, while 52% had abnormal Pap smear results. Among women with normal Pap smears who tested positive for HPV, the study found that those who tested positive for HPV strains 16 and 18 had significant risk of having advanced precancer.
“A woman who is HPV 16-positive with a normal Pap smear has a 10% chance of having a high-grade cancer precursor, so that’s worth her having colposcopy,” Stoler says.
The study was funded and designed by Roche, which manufactures the test for high-risk HPV strains.
Doctors Unlikely to Stop Using Pap Tests
Despite the study’s vote of confidence for HPV screening, Stoler thinks it will probably take more research and more time to convince doctors to change the way they screen for cervical cancer, Stoler says.
“It’s a matter of society and the organizations that write guidelines giving practitioners permission to do it that way,” he says. “That’s a hard thing to move.”
HPV testing with Pap testing is an option for women over 30. However Stoler says the co-test, as it is known, isn’t widely used.
Among doctors who do use it, recent surveys show that many doctors screen their low-risk patients -- those who test negative for both HPV and have normal cells on their Pap smears -- annually instead of every three years as recommended.
“This just shows that we’re grappling, as researchers and clinicians, with how to incorporate HPV testing in our cervical cancer screening,” says Elizabeth A. Poynor, MD, gynecologic oncologist and pelvic surgeon at Lenox Hill Hospital in N.Y.
“This study gives us additional information that when we look for HPV 16 or 18 or both, it is more sensitive than actually looking at the cells underneath the microscope,” Poynor says.