Thursday, December 8, 2011

HPV testing guidelines

Abnormal Pap smear, from Hospital of Monfalcone, Italy

Many women are not aware of the HPV test. For a portion of the last decade, co-testing with Pap smears was recommended by many women health organizations, but doctors and patients were not really using it. Now it seems that was the right call as research is showing that cervical cancer cases are not being more readily identified with co-testing.

Guidelines were recently updated for both HPV testing and Pap smears, including reinforcing evidence for delaying the time between Paps to 3 years in women who were previously negative for neoplastic changes. 

Why test for HPV?

Human papillomavirus (HPV) is a sexually transmitted virus that can cause cervical cancer in women and genital warts, or occasionally some other forms of cancer, in both men and women. A test is currently available to determine infection in women via samples from the cervix. In recent years, co-testing with Pap smears has been considered a useful method for detecting cervical cancer early, but new guidelines challenge this view.

HPV test overview

The Digene HPV test was approved by the FDA in 2003. It can detect the presence of HPV in the cervical cells taken during the Pap smear. In 2009, the FDA approved two new HPV tests, Cervista, that are capable of more specifically genotyping the high-risk HPV strains associated with cervical cancer. The tests are generally used in women over the age of 30 years because women who are younger than 30 tend to resolve HPV infections on their own (transient infection). Persistent HPV infections are associated with cervical cancer, and most infections do not result in cancer, so being positive for HPV, even the high risk strains, is not a clear cut certainty of cancer (the National Cancer Institute found that women infected with HPV 16 or 18, the high-risk strains for cervical cancer, only have a 20% risk of cancer progression over 10 years).

Co-testing and the old guidelines

Once the HPV genotyping test was available, women’s health groups and clinics began a policy of co-testing in women over 30 years of age. When a woman went to the doctor for her annual Pap smear, they would also run an HPV test. Women with positive results on both were considered to be at high risk of cervical cancer. If both tests were negative, the woman would not need another test for 3 years. If only the HPV test was positive, annual Pap smears were recommended. In 2006, the American Journal of Obstetrics & Gynecology recommended specifics based on the age of the woman, including colposcopy (a process of the doctor viewing the cervix) to confirm positive results on both tests. The clinicians and doctors felt that this would aid in earlier detection, diagnosis, and intervention, as well as cut down on unnecessary Pap testing. However, these guidelines were based on expert consensus rather than scientific studies.

New HPV testing guidelines based on medical studies

In May 2011, the National Cancer Institute reported on a large-scale study that confirmed the 3-year interval guidelines for Pap testing, finding that it did not change a woman’s risk of later cancer diagnosis compared to annual testing. They also found that the HPV test is more sensitive than the Pap smear for detecting the risk of cancer development. The researchers' recommendation was that HPV testing can be carried out as a first step – women who are positive can then have a Pap test and those who are negative can return in 3 years for another test. However, changing physician habits is difficult, and HPV is a very common virus – so in June 2011 a number of women’s health and cancer groups recommended HPV co-testing every 3 to 5 years with Pap testing remaining the first step. However the U.S. Preventative Services Task Force found limited evidence supporting HPV co-testing; in fact, they are quoted by the Washington Post as warning against the HPV test as causing more harm than benefits, especially since it does not increase the rate of diagnosis according to the accumulated medical literature (which is at odds with the study reported by the NCI in May). Many doctors have not yet embraced HPV testing, and its current recommended use is as a follow-up to inconclusive Pap smear results, so following the Task Force's recommendations will likely be easier for both doctors and patients anyway, and likely will not significantly affect cancer diagnosis.

New Pap testing guidelines (2011)

In addition to the new findings regarding HPV co-testing, studies have also found that Pap smears in women over the age of 65 who have been previously screened, and found negative, for cervical cancer are not likely to benefit the patient. As such, the U.S. Preventative Services Task Force recommends against screening in patients over the age of 65 who had previously been screened by Pap tests with negative findings. The Task Force also officially recommended the 3-year break between Pap tests for women who have consecutive negative findings, with testing starting at the age of 21 years or within 3 years of first sexual contact.


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