Study Examines Efficacy Of Cervical Cancer Screening Methods

Main Category: Cervical Cancer / HPV Vaccine
Article Date: 29 Oct 2009 - 3:00 PDT

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According to a study published Wednesday in the Journal of the American Medical Association, conventional Pap tests, which have been used since the 1940s, and ThinPrep, a test approved in 1996 that represents 70% of the U.S. cervical cancer market, are equally effective at detecting precancerous cells, USA Today reports. The main difference in the tests, according to USA Today, is how cells are prepared for evaluation (Rubin, USA Today, 10/28). Cells are smeared on a slide for evaluation in a traditional Pap test, while ThinPrep uses liquid-based cytology, wherein cells are rinsed in a vial of preservation solution (Reinberg, HealthDay/U.S. News & World Report, 10/27).

Study authors noted that FDA has allowed Hologic, the maker of ThinPrep, to say that the product is more effective in finding early and more advanced signs of cervical abnormalities (USA Today, 10/28). To test this assertion, the study authors randomly assigned 89,784 Dutch women to have either a traditional Pap test or a ThinPrep test (HealthDay/U.S. News & World Report, 10/27). George Sawaya, an ob-gyn at the University of California-San Francisco, said the study's findings "should serve as a cautionary tale that just because something is new doesn't mean it's better."

Mark Schiffman and Diana Solomon of the National Cancer Institute wrote in an accompanying editorial in JAMA that although ThinPrep is the more expensive alternative, it "is preferred by most laboratories because the specimen is easier and quicker to scan under the microscope."

Lead study author Albertus Siebers of the Radboud University Nijmegen Medical Centre said other factors, including the ability to use ThinPrep samples to test for human papillomavirus, have reduced the use of traditional Pap tests. In the new study, only one of 300 ThinPrep tests had to be redone, compared with one in 100 conventional Pap tests (USA Today, 10/28).

According to Schiffman, however, all types of routine Pap testing could eventually become obsolete because the ability to prevent and screen for cervical cancer is changing. He said, "We now have vaccines that are going to keep getting better, and we have HPV testing, which is even more sensitive than Pap smears." He forecasted major changes ahead for cervical cancer screening, "with the powerful sensitivity of doing HPV testing plus a Pap smear that is optimally done no more than every three years starting at age 30." However, he noted it remains to be seen whether women would accept a shift to testing every three years (HealthDay/U.S. News & World Report, 10/27).

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