A Pap smear, which tests for cervical cancer, has become an automatic part of the annual checkup for most women over 18. That could be a problem, though, according to researchers at the VA Outcomes Group in Vermont and Dartmouth Medical School in New Hampshire, who say millions of women are being given the test unnecessarily.

What the researchers wanted to know: Are women who have had their cervix removed in a hysterectomy being given routine Pap smears even though they serve no purpose?

What they did: The researchers used data collected between 1992 and 2002 in a telephone survey by the Centers for Disease Control and Prevention that asked more than 188,000 women if they had undergone a hysterectomy and a Pap smear within the past three years. Using other data sets, the researchers estimated the number of women for whom a Pap smear would have been justified—those who had the test before surgery, those who did not have their cervix removed, and those who had abnormal growths on their cervix. The rest, left without a cervix after surgery, were given Pap smears presumably to test for cervical cancer despite having no risk of the disease.

What they found: Up to 10 million women who have had a hysterectomy are being screened unnecessarily. Even after the U.S. Preventive Services Task Force, part of the Department of Health and Human Services, recommended in 1996 against screening women who have had a hysterectomy, about 46 percent of women still underwent needless screening after their hysterectomy.

What the study means to you: A Pap smear may not always be a good idea—particularly if you have undergone a hysterectomy. A woman who no longer has a cervix but does get a Pap smear is actually being screened for vaginal cancer, which is extremely rare. The authors were unsure why so many women are undergoing unwarranted Pap smears but wrote that it may have something to do with physicians who worry what their patients will think if they don't suggest the test or with hospital administrators who set quotas on the number of people who must be screened. It could also have something to do with people's perception that all cancer screening is worthwhile—which is not always the case, the authors point out.

Caveats: The authors used survey data to estimate trends throughout the entire U.S. population and combined data from several studies to eliminate women whose Pap smears had been needed. So, as with all surveys, their estimates are likely to be a little off. But the authors tried to overestimate the number of women with hysterectomies for whom a Pap smear was needed, so they say their estimates, if anything, tend to understate the problem of unnecessary Pap smears. Another potential problem is that some women, when asked if they have had a recent Pap smear, will lie and say they have because they think they should have had one.

Find out more: U.S. Preventive Services Task Force: http://www.ahrq.gov/

Read the article: Sirovich, Brenda E., Welch, H. Gilbert. "Cervical Cancer Screening Among Women Without a Cervix." Journal of the American Medical Association. June 23, 2004. Vol. 291, No. 24, pp. 2990-2993.

Free abstract online at http://jama.ama-assn.org/