NEW YORK - Doctors are testing women for human papillomavirus, or HPV - some strains of which have been linked to cervical cancer - more often than guidelines recommend, according to a new US study.

Not only is it a waste of money, it also means that women who test positive may be getting extra treatment they don't necessarily need and that comes with a risk of complications and side effects, added the study, published in Obstetrics and Gynecology.

In young women, a positive test gives little information, since HPV is common in women in their 20s and probably won't lead to cancer, added the researchers, who were led by Mona Saraiya of the Centers for Disease Control in Atlanta.

"There's a much greater emphasis on avoiding a single cancer versus literally thousands of women being over-screened and over-treated," said Philip Castle from the American Society for Clinical Pathology in Chicago, whose commentary on the study was published with it.

There are about 40 different strains of sexually transmitted HPV, according to the Centers for Disease Control, and at least half of sexually active people will get HPV at some point. Some strains have been linked to cervical cancer, while others cause genital warts.

Saraiya and colleagues analyzed data from a national survey of doctors and clinics that use Pap tests. In total, 376 doctors and another 216 outpatient clinics responded to survey questions about whether and how they performed HPV testing.  

Three-quarters of doctors and clinics had ordered an HPV test at least once, with more than half of those saying they used HPV testing regularly along Pap smears in women less then 30 years old - a use not recommended by the American Cancer Society and other organizations.

The majority also reported using HPV tests as a follow-up to a questionable Pap smear when the tests may not have added much information.

Finally, almost one-third of doctors and clinics who did HPV testing used two different kinds of HPV tests -- the so-called "high-risk" and "low-risk" HPV tests, even though the low-risk test tells nothing about cervical cancer since it screens for non-cancer causing strains, researchers added.

Doctors may be confused about which tests to order if they aren't keeping up with current evidence, Castle said.

"The low-risk test really has no business being on the market at all," he told Reuters Health.

With regard to testing in women under 30, he added that cancer is quite rare in that group. Routine HPV testing at that age could lead to biopsies and cancer treatments that aren't really necessary - along with a lot of stress and worry.

"There's a lot of HPV and very little disease" in women in their 20s, he said.

"The disease that's found there is generally about 10 to 15 years away from becoming invasive. There's no good justification for using" the HPV test routinely, Castle added.

But he said that the HPV testing can be beneficial for routine cancer screening in older women and to clarify some types of "equivocal" Pap smears.