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Popular Pap Test May Cause False Results

Birth Control Pills Might Make Healthy Cells Look Abnormal

The Appearance of HPV continued...

In his study, Nuovo and his colleagues initially reviewed ThinPrep Pap tests from nearly 1,000 women taking birth control pills and compared the rates of atypical results with 1,200 women not taking oral contraceptives. The pill-takers had twice the rate of abnormal Paps test suggesting the presence of HPV.

"It meant that either oral contraceptives put a woman at higher risk for developing abnormalities in her cervix, or that the testing method was somehow causing healthy cells to mimic virus-infected cells," he says. Going on the latter theory, he re-analyzed the data on 84 Pap smears indicating HPV. Only one in three actually had abnormal cells.

Still the Top Test

Still, there's no reason not to continue to use ThinPrep, say two experts not involved in the study.

"This is an interesting observation," says William T. Creasman, MD, of the Medical University of South Carolina and a spokesman for the American College of Obstetricians and Gynecologists.

"What it may do is get the labs to look at their data and see if, in fact, this is a phenomenon that is universal or something unique in this particular group," he tells WebMD. "If it is something beyond this group, it could have some clinical implications because then you're doing a heck of a lot more than you need to because you have a lot of false positives."

Most women who currently have abnormal Pap tests are retested (often with the same type of smear), and/or given a specific HPV test or undergo a colposcopy, a visual examination of the cervix.

Kenneth Hatch, MD, chairman of obstetrics and gynecology at the University of Arizona College of Medicine and president of the Society of Gynecologic Oncologists, tells WebMD that despite the finding, the ThinPrep test will continue to be the Pap smear favored by most doctors.

"It's been a major breakthrough in cervical cancer screenings," he tells WebMD. "The majority of clinicians in the U.S. use ThinPrep because it offers increased sensitivity over others in identifying lesions."

"This is an observation that may or may not have bearing," says Hatch. "But like any observation, it needs to be verified before we say it is inherent of the test as opposed to the interpreter. All Pap tests are looked at by human eyes."


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