In a 12-year study of more than a million women in the Kaiser Permanente of Northern California system, researchers concluded that the HPV screening test alone may be enough to detect the vast majority of cancers and so-called “pre-cancers” without the added second test known as the Pap test. In the study, women received both tests. The study examined patients who had cancer or pre-cancer to determine whether their disease would have been missed by HPV testing alone. The release states: “Given the rarity of cancers among screened women, the contribution of the Pap test to screening translated to earlier detection of at most five cases per million women per year.”
This study concludes that double-testing or co-testing is only protecting a tiny minority of patients, and that a single HPV test may be enough. Even though economics is part of the reason for the study, the release does not tell us how much money might be saved if a single test became the standard of care.
Prevention by early detection is a key part of saving lives from cervical cancer. The Pap smear has been widely used in the United States since the 1950s. As a result, the incidence of cervical cancer has dramatically decreased. However, the fact that certain strains of human papilloma virus (HPV) caused almost all cervical cancer was not discovered until decades later. With the introduction of testing for HPV starting after 2000, the role for the Pap and HPV test has been evolving. This study addresses the question of whether it is time to abandon the original Pap test in favor of just using the HPV test — or whether both are better than either alone. The answer seems to be that the Pap smear’s days are numbered.
The release includes the idea of costs, but without using any numbers. The two mentions of cost are here:
“However, reports of rare HPV-negative, Pap-test positive cancers are motivating continued use of both tests (cotesting) despite increased testing costs.”
and here:
“Researchers were searching for realistic performance data to quantify the additional benefit of the Pap test component of cotesting, as the costs of intensive screening of all women using two screening tests are substantial.”
The readers are not given any framework in which to judge how much more co-testing may cost than single-testing by either of the methods discussed. We are also not given any society-wide idea of what we all might save if both tests were not routinely administered.
The release is comparing two different screening methods, which both have benefits, to using either one of them alone.
We were especially pleased that the release included a clear description of the benefit using absolute, rather than just a relative, risk number.
“Given the rarity of cancers among screened women, the contribution of the Pap test to screening translated to earlier detection of at most five cases per million women per year. Two-thirds (67%) of women found to have cancer up to 10 years of follow-up at Kaiser Permanente were detected by the first cotest performed.”
Besides this number, the release included specific numbers for benefits of each test.
“HPV-negative/Pap test-positive results preceded only small fractions of cases of precancer (3.6%) and cancer (5.9%); these cancers were more likely to be regional or distant stage than other cases.”
The release doesn’t directly explain the harms of cancer screening. The release addresses the harm of omitting one test, but this wasn’t enough to meet our standard. The release states that HPV is “more sensitive than the Pap test for detecting precancer.” But it doesn’t discuss the flip side, which is that many pre-cancers may not go on to become cancer even though all are treated.
The release frames the study done by Kaiser Permanente of Northern California as “the most extensive experience of HPV testing incorporated into routine screening in the world.”
More than a million women were tested since 2003. There were 623 cancers and 5,369 pre-cancers. Researchers examined these to judge the relative contribution of the Pap and HPV test to identifying cases.
These details give readers plenty of information to judge the quality of evidence.
The funder (NIH/National Cancer Institute) is listed on a sidebar of EurekAlert! where the release is hosted. We encourage releases to also include funders in the release itself. There do not appear to be any conflicts.
The release is about comparing alternative screenings, either co-testing or HPV alone. The report does not address Pap alone (recommended for women under 30 years old).
It is implied that these tests are widely available in the US.
The release addresses novelty with this summary of the work: “the most extensive experience of HPV testing incorporated into routine screening in the world.” The long-term study comparing outcomes from two long used screening tests is novel.
We found no unjustifiable language.
Systematic, Criteria-Driven
Monday at #ADA2021, an infectious disease epidemiologist, a journalist, and a researcher shared perspectives on communication of risk in the era of COVID-19: http://ow.ly/ROfR30rMeE7 @AstleyCM @garyschwitzer @berthahidalgo @ADA_DiabetesPro
Shoutouts to @susan_bewley @drkevinknopf @MichaelBaum11 in this call for more than fawning coverage from press releases for these kinds of stories.
Also, linked history inside goes back 5 years just on Grail apparently trying to become Holy Grail. https://twitter.com/garyschwitzer/status/1408849696416841731
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