HPV test more accurate than Pap smear

"Doctors are telling us tonight [that] a new test could replace the Pap smear for detecting cervical cancer."

"A test to detect human papillomavirus (HPV) -- which causes most cervical cancers -- was far better than the standard Pap smear at catching malignancies," according to two new studies published in today's issue of the New England Journal of Medicine. HealthDay continues, "Pap tests have been the standard screening test for cervical cancer for the past 60 years. More recently, the liquid-based or thin-smear Pap test was developed, and it was initially thought that this newer technology would offer significant advantages over the traditional Pap test." But studies have not shown that the newer Pap test is significantly better. Since "most cervical cancers are caused by HPV, the test to detect HPV infection is also an option for screening in addition to the Pap test." The studies published today sought to compare these tests.

Marie-Hélène Mayrand, M.D., of McGill University in Canada, and colleagues, "assigned 10,154 women, ages 30 to 69, to one of two groups -- a 'focus on Pap' group, which got a Pap smear followed by the viral test, and a 'focus on HPV' group, which got the HPV test first, followed by a Pap smear." The trial lasted from September 26, 2002 through February 3, 2005. They "found that the viral test...correctly identified cervical intraepithelial neoplasia (CIN) of grade two or three 94.6 percent of the time, compared to 55.4 percent for the Pap test." However, "the specificity of the viral test was 94.1 percent, compared to 96.8 percent for Pap testing." For the second study, conducted between May 1997 and November 2000, "Swedish researchers randomly assigned 12,527 women ages 32 to 38 to get a Pap test (and form a control group) or a Pap test combined with a test for...[HPV] using polymerase chain reaction." They found that "[a]t baseline,...the proportion of women in the two-test group who had CIN2, CIN3, or cancer was 51 percent higher than among the women who only got the Pap test." However, "at the subsequent screening, following treatment where appropriate, the rate in the two-test group was 42 percent lower than in the control group." The researchers attributed "[s]ome of the differences" to "over-diagnosis at baseline."

"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." Since "a lesion can take a decade or more to turn into cancer, annual Pap testing usually finds precancerous lesions in time." While "[t]he HPV test is considered a useful addition to Pap testing for women over 30 who may be at high risk for cervical cancer,...the Canadian study is the first North American trial to assess its value as a stand-alone test."

"The new test could replace the...Pap in a matter of years, experts say." Furthermore, women "won't need a screening test as often." The AP continues, "The HPV test has been available in the U.S. since 2000, and was first used for inconclusive Pap tests. Now women over 30 can get a HPV test -- but only along with a Pap -- and wait three years to be tested again if both tests are negative." Currently, scientists are attempting to determine "whether the HPV test can be used alone, and whether it can prolong the intervals between exams." Debbie Saslow, "director of breast and gynecologic cancer for the American Cancer Society, said [that] evidence from a number of studies supports using the HPV test in place of a Pap."

Meanwhile, the Wall Street Journal (10/18, D6, Tomsho) points out that cervical cancer is "[f]ar more common in developing countries," and "is the second most common cancer among women world-wide, with nearly 500,000 new cases and 290,000 fatalities a year." In the U.S., however, "screening has sharply reduced cervical cancer," and "there are about 11,000 new diagnoses and 3,700 deaths a year."

"One concern about the HPV test has been a higher rate of false positives due to its superior sensitivity, but [the Canadian] study found only a small difference between the two screening tools." Eduardo Franco, Dr.P.H., co-author of the study, "calls the increased rate [of] false positives, which could lead to unnecessary additional testing, a fair tradeoff for detecting far more cervical pre-cancers -- 94 percent vs. 55 percent -- and, probably, allowing women to screen less frequently." USA Today further notes that the FDA has approved one HPV test "only for use in women over 29 as a follow-up to inconclusive Pap smear results or as a 'co-test' done at the same time as a Pap smear." It is "made by Digene of Gaithersburg, Md." Currently, the FDA has not approved any "stand-alone primary screening test[s]."