Commentary: New Tests for Cervical Cancer Unwarranted
Nov. 17, 1999 (Atlanta) -- New tests promising increased accuracy of Pap
smear laboratory analysis have not been backed up by rigorous science and could
be misleading the public, according to an analysis of previous research studies
published in a recent issue of the medical journal Obstetrics and
The researchers who analyzed the studies say that advertising aimed directly
at consumers "preys on the fears of women" by implying that they should
be demanding new laboratory methods for detecting cancerous or precancerous
cells taken from the cervix.
Instead, they say, according to the studies, the tests -- in addition to
being more expensive than traditional Pap smear analysis -- so far have not
shown a clear superiority.
"The biggest risk of cervical cancer is [that of] not getting screened
at all," co-author David Grimes, MD, tells WebMD. "The risk of missing
a cancer is exceedingly remote. It's not the fallibility of Pap smears, it's
just that people don't get them." Grimes is clinical professor of
obstetrics and gynecology at the University of North Carolina at Chapel
According to a 1996 report by the National Institutes of Health, about
15,700 U.S. women are diagnosed with cervical cancer every year, and nearly
5,000 die annually. The report notes that about 50% of women who develop
cervical cancer have never had a Pap smear test.
"We don't need to screen the same women better," says researcher
George Sawaya, MD. "We need outreach to women who don't get screened. Most
women who've been screened often in their lifetime will never get to the point
of getting cervical cancer."
When detected in time, precancerous lesions on the cervix can be removed or
otherwise inactivated before tumors develop.
With the new testing technology, after a cervical-tissue sample (Pap smear)
has been obtained, the cells are captured in a liquid formula -- which provides
more cells for analysis -- instead of being placed on a "dry" slide for
evaluation. But after reviewing the clinical studies that preceded FDA approval
of the new testing method, the researchers found similar rates of accuracy --
and "scant evidence [the new tests] are better."
The problems inherent in Pap smear tests are 1) whether the sample is large
enough to include infected cells and 2) whether the tissue samples are
correctly interpreted, says Sawaya, who is an assistant professor of obstetrics
and gynecology at the University of California, San Francisco. Currently, up to
25% of traditional tests result in false-positive or false-negative diagnoses,
which has led to a standard practice of retesting in many cases.
But the researchers' analysis of the comparisons made between traditional
testing and newer methods found no way to determine whether "increases in
the number of positive tests merely represent increases in
"Because tests can be inaccurate, frequency is advised," says
The American College of Obstetricians and Gynecologists recommends that
women begin having Pap smears at age 18 or when they become sexually active.
Cervical cancer is caused by the sexually transmitted disease known as human
Cervical cancer develops over a long period of time, providing numerous
chances to detect it before tumors become apparent. But the cancer develops
without obvious symptoms. Sawaya says incidents of abnormal vaginal bleeding
should signal a need for gynecological evaluation.
Grimes also recommends frequent tests, but he says that there are no
standards that fit all women. "Screening should be tailored to the
individual patient and should be discussed with a clinician. There is no 'one
size fits all' for who should be tested and when."