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A key federal advisory panel on Wednesday said it will not endorse HPV screening for cervical cancer and favors giving Pap tests only every three years in women between ages 21 and 65.

The U.S. Preventive Services Task Force said it recommended against testing for human papillomavirus, or HPV, in women younger than age 30, and said there was insufficient evidence to justify it for women over age 30. In expressing skepticism of the tests, it said "the current evidence is insufficient to assess the balance of benefits and harms of HPV testing, alone or in combination with" Pap tests.

The task force recently triggered controversy by recommending against the use of a blood test for prostate cancer in healthy men. The current set of recommendations will not likely generate that level of heated debate. But they come as U.S. medical practices are increasingly using such tests to fight cervical cancer, which is caused by some forms of HPV.

Women have become accustomed to getting annual Pap tests, and HPV testing to help detect precancerous conditions is being more widely used. A July article in Obstetrics & Gynecology said that more than half of the medical practices surveyed had used HPV testing, including in women under age 30 -- a practice the federal task force seeks to discourage.

The task force concluded that, compared with the Pap tests alone, HPV tests were more likely to produce "false-positive" tests results and could lead to "unnecessary diagnostic procedures, treatments, and the consequent harms may increase." The American Cancer Society has recommended women get HPV tests in addition to Pap tests, said Debbi Saslow, its director of breast and gynecologic cancer. The cancer society is expected to announce its own new recommendations Wednesday.

Dr. Michael LeFevre, a member of the task force and a professor of family and community medicine at the University of Missouri in Columbia, acknowledged that recommending a Pap test only every three years, and only for women ages 21 to 65, is different than some doctors' practice.

Yet, he said, with Pap tests every three years, "The same benefit is achieved as annual testing with less burden on the woman, not just the inconvenience and discomfort of the initial Pap smear but more importantly, the dealing with false positive tests and the associated testing and treatment that follows."

Cervical cancer has declined dramatically in the United States, from nearly 15 cases for every 100,000 women in 1975 to nearly 7 per 100,000 in 2008. About 12,200 new cases and 4,210 deaths from the disease occurred last year, most of them in women who have never been screened or not in the past five years.

The American Cancer Society and other groups say using Pap smears together with tests for HPV, the virus that causes cervical cancer, could improve screening. But the task force concluded the evidence is insufficient "to assess the balance of benefits and harms" of that.

Here are some questions and answers about the cervical cancer guidelines.

Q. At what ages should screening start and end?

A. The task force recommends against screening women under 21 or older than 65. Very few cervical cancer cases occur in women under 21, so the old advice to start screening three years after the age of first intercourse has been changed. HPV tests are only approved for women after age 30 because transient infections that don't pose a cancer risk are more common at younger ages.

"We should not be screening teenagers. It's not helping, it's not finding any more cancers and it's creating way too many harms for them," Saslow said.

Q. Should anyone else not be screened?

A. Women who have had their cervix and uterus removed should not be tested, but check with your doctor - not all hysterectomies are complete; some leave the cervix.

Q. What does screening cost?

A. Paps cost $15 to $60; HPV tests run $50 to $100.

Q. Will insurance pay for HPV tests since the government panel doesn't endorse them?

A. Probably. They are included in preventive services that other federal advisers say should be covered under the Affordable Care Act, and the government has continued to pay for mammograms for women who want them even if it is sooner or more often than the task force recommends.

Q. What if I've had the HPV vaccine?

A. Doctors don't know how the vaccine will affect HPV test results or how long the vaccine lasts, so women should still be screened for cervical cancer if they are within the recommended screening ages.

The Wall Street Journal and the Associated Press contributed to this article.