Newer Isn’t Always Better: Pap Smear Version

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Over the last 15 years, the vast majority of American gynecologists have switched from using the traditional “pap” smear to screen for cervical cancer to another screening method called “liquid based cytology” (women may know the test by the popular brand name, ThinPrep).  But a new study of nearly 90,000 women in Holland finds that the newer test is not more effective than the traditional pap smear—and it is significantly more expensive.

In the study, published in the Journal of the American Medical Association, some doctors were randomly assigned to use traditional screening while others used the newer method.  No significant differences were found in terms of false positive or false negative results.  ThinPrep is known to be more expensive than traditional testing but there isn’t an accurate way to compare prices because health groups negotiate different prices, based on volume.

Mark Schiffman, MD, PhD, a senior investigator at the National Cancer Institute, is the lead author of an editorial that accompanied the study.  He notes that the newer method can be easier to read because it is standardized and it does allow for the same sample to be tested for HPV, which can’t be done with the older one.

“It’s highly unlikely that in US will change back,” he says, “The broader issue is that everything is changing. The big question in the US will be how does vaccination [for HPV] change screening?  How does the introduction of HPV testing as a more sensitive screening along [affect the way we screen]?”

Schiffman says that women and gynecologists have both become reliant on the annual pap smear and may see moves to less frequent screening as cost cutting, rather than related to changes in the research on what is needed.

“Lots of doctors want to see their patents every year,” he says, “It will be very interesting watch. It’s an engrained social good: we’ve driven down cervical cancer rates by repeated screening.  The pap test is one of greatest screening programs ever. Now, there is an even more accurate combination that could extend the interval between testing. How do we transition without messing it up?”

The fact that this study found that there is no difference in effectiveness between the newer and older screening methods—which were originally claimed to be more accurate—suggests one part of the answer.  That is, we need to make sure there is good data driving any decision about screening.

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