In 2003 the U.S. Preventive Services Task Force (USPSTF) published recommendations for cervical cancer screening. To inform an updated recommendation, researchers performed two reviews of the published literature focusing on evidence that has become available since the 2003 recommendation.
The first article reviewed published articles comparing liquid-based cytology to the conventional Pap smear. With a conventional Pap smear, the clinician collects cells from a woman's cervix and transfers them to a slide for microscopic evaluation. With a liquid-based test, cervical cells are preserved in fluid, rather than smeared directly onto a slide. The same sample can be used for HPV testing.
The researchers found that conventional and liquid-based pap tests did not differ substantially in measures of relative detection or absolute sensitivity or specificity for detection of precancerous cells. However, the liquid-based test produced fewer unsatisfactory slides than conventional testing. Available evidence, though minimal, suggested no substantial difference in harms between the two tests.
Researchers also reviewed published research to assess the benefit and harms of HPV testing in women 30 years and older as an alternative or adjunct to conventional cytology screening. They found that HPV testing was more sensitive than cytology, but there was reduced specificity. While HPV-enhanced screening strategies offer a potential cancer prevention benefit compared with Pap testing alone, there is insufficient evidence to justify substituting HPV for cytology at the population level.
In terms of HPV-screening harms, false positive screening results and diagnosis of regressive or non-progressive histologic pre-disease could result in harms from unnecessary procedures or overtreatment. In addition, women diagnosed with HPV (especially young women for whom the disease may clear on its own) may experience unnecessary anxiety. At this time, researchers need more evidence in order to understand the population impact of HPV testing as a cervical cancer screening tool.
A second review focused on the appropriate ages at which to begin and end cervical cancer screening. Because cervical cancer is rare among women under the age of 20, the research supports beginning screening at age 21. If a woman aged 65 or older has had adequate recent screening with normal Pap smear result and is not at otherwise high risk for cervical cancer, the research suggests that she can end screening age 65.
The evidence reviews have been used to develop a draft recommendation statement that will be posted to the USPSTF website for public comment on October 19th. The final recommendation will be published in Annals at a later date.
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