Best Cancer Test: HPV vs. Pap Smear
Study Shows HPV Test Is Better Predictor of Cervical Cancer in Older Women
Nov. 2, 2006 -- For more than 60 years the Pap smear has been the screening
method of choice for cervical cancer, but it is not the best approach for
assessing risk in older women, new research suggests.
Findings from a large, Danish study provide compelling evidence that testing
for human papillomavirus (HPV) is more effective for identifying older women
with a high risk of developing cervical cancer.
Cervical cancer is caused by HPV infection, which is spread through sexual
contact. Two specific types -- HPV 16 and HPV 18 -- are believed to be
responsible for up to 70% of cases worldwide.
HPV is fairly common among younger women, but in most cases infection is
transient and does not pose a health risk.
Infection tends to be rarer and more persistent in older women, however, and
infection later in life is increasingly recognized as a major risk factor for
In the newly reported study, women between the ages of 40 and 50 who tested
positive for HPV had a greater than 20% chance of developing cervical cancer
within 10 years. Most of these older women with positive HPV tests had
concurrent Pap smear results that were negative.
"We have documented that a single HPV test can actually predict older
women at risk for cervical cancer better than a single Pap smear can," says
researcher Susan Kruger Kjaer, MD.
"Based on these results, we feel that an HPV test would benefit older
women, whether or not that test is used in conjunction with Pap smears, or used
by itself as an initial screen."
Better Long-Term Predictor
Kjaer and colleagues from the Danish Cancer Society compared HPV and Pap
smear screening in two Danish populations -- 8,656 women between the ages of 22
and 32, and 1,578 women between the ages of 40 and 50.
Cervical samples were collected from all of the women for HPV testing, and
they all had multiple Pap smear tests over 10 years of follow-up.
In a pap test, cells from a woman's cervix are sampled and examined under a
microscope for abnormalities.
Twenty-one percent of the older HPV-positive women with negative Pap smears
developed cervical cancer or precancerous cervical lesions within 10 years,
compared with just 1.7% of women who tested negative on both screening
As expected, HPV infection was more common in the younger women (17%) than
in the older women (3%). And the older women who tested positive for HPV tended
to have more severe cervical abnormalities than the younger women.
The study is published in the Nov. 1 issue of the journal Cancer
The American Cancer Society (ACS) recommends that all women begin having
annual Pap test screening within three years of having vaginal intercourse, but
no later than 21 years of age.