Unnecessary Pap Tests in Millions of US Women

Zosia Chustecka

January 04, 2013

In their report on cervical cancer screening released yesterday, the Centers for Disease Control and Prevention (CDC) startlingly estimated that 22 million women in the United States may have undergone such screening unnecessarily, because they had already had hysterectomies.

An expert approached by Medscape Medical News to comment on the issue cautioned that the data collected by the CDC were from women self-reporting and so may be subject to bias. She also suggested that some of the unnecessary testing, which is contrary to guidelines that have been in place for a decade, may be due to confusion stirred up by educational campaigns for the human papilloma virus vaccine Gardasil (Merck & Co).

The CDC analyzed data collected from 2000-2010 by the Behavioral Risk Factor Surveillance System on screening for cervical cancer using the Papanicolaou (Pap) test.

In one of the articles published in Morbidity and Mortality Weekly Report, the CDC highlighted the fact that during the study period, screening in women after a hysterectomy had declined from 73.3% in 2000 to 58.7% in 2010. But this means that more than one half of the women were undergoing Pap tests unnecessarily, because hysterectomy involves removal of the cervix in the majority of cases (94% of cases, the CDC estimates).

Such women do not need cervical cancer screening — and it has been specifically discouraged in guidelines from all the major organizations since 2002-2003.

Several media reports highlighted this finding and emphasized the huge waste of financial resources this involves.

The CDC itself commented that in this population, any benefit from screening "might be outweighed by the net harm." Such harm may include false-positive tests leading to needless patient anxiety and invasive procedures.

"The false-positive rate...is indeed a great potential harm to women and cost to the healthcare system," says Diane Harper, MD, MPH, professor of community and family medicine/obstetrics and gynecology at Dartmouth Medical School, in Hanover, New Hampshire, and director of the Gynecologic Cancer Prevention Research Group at the Norris Cotton Cancer Center.

Medscape Medical News approached Dr. Harper to shed some light on some of the findings from the survey.

Self-Report Data Are Subject to Bias

Dr. Harper emphasized that the data are based on self-reporting, and thus are subject to bias.

"We have ample evidence to show that women of all ages are not cognizant of what a Pap test is," Dr. Harper said. "Most women believe that anytime they have an examination of the pelvic area, whether a speculum was used or not, they had a Pap test."

This has been shown in multiple research studies, and it raises questions concerning the validity of the self-report nature of the CDC survey, she said. "Hence, what is really being compared is whether women's perceptions of having had a Pap test have changed with the new guidelines."

"The second issue with the CDC survey data," she continued, "is that the answers women can choose for frequency of Pap testing are hard for women to internalize. Most women can distinguish 'never' from 'ever.' And most women can distinguish within the past 12 months/year. But at frequencies longer than a year, there is very poor recall accuracy, leading to tremendous bias how the data are interpreted."

Merck Education Created Confusion

Commenting specifically about the data on Pap tests done after hysterectomy, Dr. Harper puts some blame onto the Merck advertising/educational campaigns for Gardasil, which emphasize how human papilloma virus (HPV) is related to vaginal, vulvar, anal, and cervical cancers. These campaigns have "left most of the population and many ob/gyn as well as primary care doctors very confused about how to detect these increasingly more common HPV-related cancers," she told Medscape Medical News.

"It does not surprise me that physicians have taken a woman's risk for HPV exposure (number of sexual partners or past HPV infection) and stated that even with a hysterectomy for reasons other than HPV, there is no other way than a Pap test to determine if a vaginal cancer is beginning. There are a number of incorrect assumptions in that line of thinking, but that line of thinking has been spawned after the intense advertising campaign Merck undertook for their HPV vaccine," she said.

In its report, the CDC also mentions vaginal cancer as a reason cited by proponents of continued screening after hysterectomy. "However, vaginal cancer is rare, and the value of cytology tests to detect vaginal cancer in the absence of a cervix is unknown," the agency points out.

Unnecessary Testing in Other Groups

The CDC survey also highlighted several other groups of women who are undergoing cervical cancer screening unnecessarily and contrary to guidelines.

Although there had been some variation in recommendations made by different organizations in the past, updated guidelines released last year saw a convergence of opinions and very similar recommendations issued by the American Cancer Society, the American College of Obstetricians and Gynecologists, and the US Preventive Services Task Force.

In the new guidelines, there were specific recommendations that cervical cancer screening should begin at age 21 years, and not before, and yet data from the CDC survey suggest that Pap testing is being carried out in 18- to 21-year-olds.

That may not be the case. Dr. Harper explained that what these young 18- to 21-year-old women were reporting as a Pap test may actually have been a test for chlamydia, "which is prime in this age group."

Although it can be tested via urine, a chlamydia test is often done via a cervical sampling (ie, by a pelvic examination with a speculum), she explained. "Hence, a woman 18 to 21 who was being screened for chlamydia may have reported that she also had a Pap test done, not really knowing whether she did or not. Most of the time, the nurse practitioners or physicians who do the sample collection only report back that the results are 'normal' and not specifically that a chlamydia test was negative and a cytology test showed no abnormal cells."

"The other 'quiet' reason is that the incidence of cervical cancer in the US in women under the age of 21 is 1.7/100,000. This is a real number, and this means that real young women get cervical cancer, and some of them die," Dr. Harper added.

"However, cytology is only good enough to reduce cervical cancer to 2.8/100,000, so getting Pap testing does not allow us to detect this small but real number of young women with cervical cancer. Adding HPV testing to cytology in this age group just creates a very large number of false positives. Hence, the reality is that we have no perfect system — Gardasil can only reduce the cervical cancer rate to 14/100,000, which is worse than Pap screening and not a way to protect all of the 1.7/100,000 young adolescents from cervical cancer. Hence, we accept that some cervical cancers will not be detected," she said.

Practice Changes Take Time

Another finding from the CDC survey was data suggesting that women in the 22- to 30-year-old age group were undergoing Pap tests annually instead of every 3 years, as per the new, updated guidelines.

This as well as some of the other findings suggest that it is taking some time for recommendations in the guidelines to filter through to clinical practice. Dr. Harper offers a few suggestions as to why this is the case: physicians may not be understanding the evidence for the change in the screening recommendations; reimbursement for the test still occurs; the patient feels at risk and requests frequent testing ("or the same testing as my sisters had..."); and nursing staff may set up the clinic rooms not understanding or accepting the change in guidelines.

"All past analyses have shown that it takes about 10 years for physician behaviors to change to reflect the latest change in screening recommendations," Dr. Harper noted.

Also approached for comment was Maurie Markman, MD, vice president of patient oncology services and national director for medical oncology at the Cancer Treatment Centers of America, and clinical professor at Drexel University College of Medicine, Philadelphia, Pennsylvania. Dr. Markman writes the Markman on Oncology blog for Medscape Medical News.

"There are a number of possible explanations for why physicians continue to obtain Pap smears in settings where the evidence suggests limited utility," he explained. First, "individual physicians have been obtaining these tests routinely in these groups in the past, and it may not be easy to change existing practice patterns," Dr. Markman noted. In addition, "other 'screening' tests are obtained yearly (mammogram) and it may be easier to organize all such testing at the same time," he said. Also playing a role are patient requests/expectations and practice economics, he added.

"I believe the major point to be made is that this experience demonstrates the complexity of changing established and known effective practice, even with the firm and rational recommendation of national clinical organizations" Dr. Markman said.

MMWR. 2012;61:51,52;1038-1047.