updated 4/21/2008 4:12:39 PM ET 2008-04-21T20:12:39

With apologies to Mark Twain, reports of the death of the Pap smear are premature.

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Yes, new research suggests a test for the HPV virus that causes cervical cancer may replace the old-fashioned Pap one day as that cancer's primary screening tool. But even enthusiasts say it will take years of additional research to make such a big switch.

For now, a new trend is the Pap-plus — both a Pap and an HPV test — to improve screening accuracy. But government researchers issued a caution this month: Nearly one in 10 women over age 30 who get the combo test learns they have HPV even though their Paps show no cancer or even precancerous cells. They'll need repeat checkups, and maybe more in-depth testing, to tease out who's really at risk.

What makes the issue confusing: Women's bodies very often clear an HPV infection on their own, without lasting harm, but it can take a year. The younger the woman, the more likely that HPV is going to be transient.

"One HPV test does not tell you very much. Two consecutive HPV tests are what you need," says Debbie Saslow of the American Cancer Society, who fields phone calls from women frightened by the test mismatch.

"Right now we're, I think, in quite a state of flux," adds Dr. George Sawaya of the University of California, San Francisco, who worries that women aren't being educated enough about the pros and cons of their test options. "We are very thoughtful in telling them how we believe it can add to their care versus how it may be complicating."

Add the still-to-come impact of the new HPV vaccine, and one thing is clear: The days of simple one-size-fits-all advice on cervical cancer screening are ending — and women will need to be savvy to realize the newer technology's biggest benefits.

Cervical cancer will strike just over 11,000 U.S. women this year and kill 3,870, the cancer society predicts. Paps are credited for cutting death rates in half since the 1970s, because they can spot precancerous cells in time to remove them and prevent invasive cancer.

HPV, or human papillomavirus, is a common sexually transmitted disease. Some of HPV's dozens of strains can cause cervical cancer if a woman remains infected for a long time — more than a year, according to research in this month's Journal of the National Cancer Institute. The HPV test is designed to detect most of the worst strains, using the same cells scraped from the cervix as a Pap does, to signal who's at high or low risk.

Neither test is perfect. Paps can miss cancer signs, which is why women are urged to get them every one to three years. Cervical cancer grows so slowly that an abnormality missed at one checkup can still be caught next time.

Also, roughly 4 million of the nation's 60 million annual Paps appear abnormal but not clearly dangerous. An HPV test that finds no virus gives peace of mind that nothing's wrong, a crucial use of that test.

Finding the balance
A positive HPV test detects that virus is present, but can't measure duration of infection or actual abnormalities on the cervix, which require more in-depth follow-up testing.

"There's absolutely a tradeoff," says Dr. Diane Solomon of the National Cancer Institute. "There's that balance between wanting to identify ... young women at risk, but not overtreat."

Yet the HPV test's extra sensitivity, casting a wider net for who's at risk, is precisely what has researchers around the world furiously studying it as a potential replacement for the Pap. A list of studies in the last six months have made headlines by finding a stand-alone HPV test more accurate than a Pap at identifying women with cancer or pre-cancer — almost twice as accurate, in one study.

While that research so far has compared HPV to an older type of Pap, Canada last month began enrolling 33,000 women into a study to compare HPV testing to the liquid-based Paps most common today to see if that makes a difference.

Also, more precise HPV tests, that can pinpoint if women have the one or two most dire strains, are being developed to offer more accuracy.

An extra twist: The HPV test may prove especially useful in poor countries, where cervical cancer still strikes hundreds of thousands of women who have no access to repeat Paps and might benefit more from a less frequent viral check.

However all this research turns out, cancer groups for now stand by their guidelines:

  • Women under 30 should get a Pap alone. If it's is inconclusive, HPV testing can rule out who needs further examination. A first test should be three years after starting sexual intercourse or at age 21.
  • Women over 30 have the option of a Pap followed by an HPV test, or a simultaneous Pap-HPV combo. If both are negative, women can wait three years to be tested again.
  • Women who don't get the HPV test still can wait three years between Paps, if they've had three consecutive clear Paps.
  • Anyone who's received the new HPV vaccine still must follow guidelines for their age group. That's because the vaccine prevents some but not all HPV strains, and some teens or young women may have been infected already before they were vaccinated.

Stay tuned: The advice is almost certain to change in the next few years.

Paps are "going to be around for ... at least for the next decade," says NCI's Solomon. "But we may not be doing as many Paps in 10 years as we're doing now."

Copyright 2008 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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