HPV Beats Pap as Cervical Cancer Test
HPV Test 40% Better at Detecting Precancerous Cells
Oct. 17, 2007 - The Pap test is an annual ritual for millions of American
women, but it may not be the best way to screen for cervical cancer.
In a head-to-head comparison study from Canada, DNA testing for human
papillomavirus (HPV) was found to be far more accurate than traditional Pap
smear testing for detecting precancerous lesions.
The HPV test was nearly 40% better at detecting these lesions than the Pap
HPV testing accurately detected precancerous lesions without generating
false-negatives 94.6% of the time, compared with 55.4% of the time for the Pap
The DNA test did produce more false-positive results than Pap testing, but
the difference was not as great as some previous studies suggest.
The findings are published in the Oct. 18 issue of The New England
Journal of Medicine.
“It is clear that the HPV test picks up more precancers than the Pap test,
and I personally think it is a better test,” researcher Marie-Helene Mayrand,
MD, of McGill University, tells WebMD. “But you will certainly find doctors who
feel differently because more [false-positive] women are sent for invasive
diagnostic procedures they don’t need.”
Pap vs. HPV
The Pap test is used to screen for abnormal cellular changes that may lead
to cervical cancer. Annual testing is recommended because the test often misses
slow-growing precancerous lesions.
Because a lesion can take a decade or more to turn into cancer, annual Pap
testing usually finds precancerous lesions in time.
The HPV test is considered a useful addition to Pap testing for women over
30 who may be at high risk for cervical cancer, but the Canadian study is the
first North American trial to assess its value as a stand-alone test.
The McGill researchers followed 10,154 Canadian women between the ages of 30
and 69 who were enrolled in the study between 2002 and 2005.
Over the course of the trial, HPV testing accurately detected pre-cancerous
lesions without generating false-negatives 94.6% of the time.
A Better HPV Test
Like Mayrand, study co-author Eduardo Franco, DrPH, says the superiority of
the HPV test for identifying lesions without false-negatives argues in favor of
its use as a standalone test
“A false-positive may be very disturbing and psychologically distressing for
the patient, but in the end, she’s free of disease,” Franco notes in a news
release. “False-negatives are very serious business, however. The patient will
be assured that she is negative, all the while a pre-cancer has a chance to
become a cancer or her existing cancer has a chance to grow.”
Mayrand says the next step is improving the HPV test’s specificity, or
ability to detect pre-cancerous lesions without false-positives.
“We are working on strategies to increase the specificity of HPV testing,”
she says. “This is not the last study on the subject. I think that within a few
years we will find ways to make HPV testing more specific.”
Cervical Cancer Testing Important
Though experts disagree on the better test, the underlying message is clear:
"The most important message remains unchanged: Women should be screened
using one of three options: a conventional Pap test, liquid Pap, or Pap plus
HPV test," says Debbie Saslow, PhD, director of breast and gynecologic
cancer at the American Cancer Society. "For women who have access to HPV
testing (e.g. insured women whose plan covers the test), the HPV test offers
added benefits over [Pap tests] alone."