Not everyone’s clear on HPV tests
Most women are familiar with the Pap smear — a test that detects precancerous changes in the cells of the cervix. They’re less likely to know of the far newer HPV test, which detects the human papillomavirus, which causes cervical cancer.
Two different HPV tests — a high-risk and a low-risk test — were approved by the Food and Drug Administration in 2003. But there’s confusion over how these tests should be used. A study published in the July issue of Obstetrics & Gynecology found that 25% of doctors were giving the wrong type of HPV test, nearly two-thirds were giving the test to the wrong patients and many were testing their patients too often.
Many patients are getting HPV tests every year, which is not recommended, said Debbie Saslow, director of the breast and gynecologic cancer programs at the American Cancer Society. As a result, “a lot of women are being referred for procedures they don’t need,” she said. “In addition to being inconvenient and anxiety-producing, there can be complications.”
The Pap smear, which has a 60-year history, involves a doctor scraping a few cells from a woman’s cervix and a clinical laboratory technician then studying those cells for any abnormalities. With HPV tests, doctors analyze a swipe of cells for the presence of viral DNA. (There’s also a newer liquid-based Pap test in which cells are put into a preservative solution; that same sample can also be tested for HPV.)
The HPV test is excellent at detecting the virus’ genetic material and will pick up active or recent infections, said Dr. Amer Karam, a gynecologic and surgical oncologist at UCLA. The high-risk test doesn’t look for every strain of HPV, just the most virulent ones, especially those linked to cervical cancer.
The low-risk test, in contrast, identifies strains that cause genital warts, and the American Cancer Society and other professional organizations do not recommend it. It was green-lighted by the FDA only for safety and effectiveness — not usefulness. “That one is interesting for researchers, but has no value for doctors and patients,” Saslow said.
Still, since scientists agree that high-risk strains of HPV cause virtually all cases of cervical cancer, the high-risk test would seem to be a good early-detection method for everyone. But there are reasons why that isn’t so, Saslow said.
For one thing, HPV is a very common virus. A 2007 study published in the Journal of the American Medical Assn. found that 25% of all U.S. women had at least one strain of HPV and 15% had ones linked to cancer.
And most of the time, infection with HPV (which occurs through sexual contact) is no big deal. Usually, an infection will clear up on its own within weeks or months. In the worst-case scenario, a persistent infection can lead to cellular abnormalities, then precancerous changes and ultimately cancer. But these steps are not inevitable. Some people live with the virus without problems, and the body can repair some cellular changes.
Even when HPV does lead to cancer, it’s a long and slow process, Saslow said — 15 to 20 years. That means annual testing is overkill. Even the Pap test doesn’t have to be performed annually, as was advised in the past.
For these reasons, the test must be used judiciously — with the right patients at the right intervals. It is an option for all women aged 30 years or older, but is not recommended for younger women because infections of the virus are very common, but mostly transient, in women in their 20s.
At age 30 or so, a larger percentage of infections are of the persistent kind, so the benefits of testing start to outweigh the harms of more invasive diagnostic tests that may be needed after detecting the virus.
For example, doctors may follow up with a colposcopy — a way to look closely at the cervix during a pelvic exam — or a biopsy, in which cervical tissue is removed for further study. Cutting tissue can result in complications such as bleeding or painful periods, Karam said, and also can scar or weaken the cervix, which can cause problems with future pregnancies, such as premature labor or trouble dilating during labor.
Right now, the HPV test is generally used as an adjunct to Pap tests. For example, Karam said, if a patient’s Pap test results are ambiguous, the HPV test may help the doctor decide what steps to take next. If the virus is present, more tests may be called for, but if the virus is absent, there’s nothing to worry about.
After a negative HPV test combined with a negative Pap test, women don’t need to get screened again for three years. Some European countries use intervals of up to five years, Karam said.
The HPV test is more expensive ($80-100) than Pap smears (about $35), but is cheaper to process. If HPV testing overtakes Pap tests as a screening tool — as many doctors think will happen eventually, at least in women over 30 — the fact that screening can be done less often also should save on cost.
In third-world countries, the HPV test — a simple-to-use kit — has advantages compared with Pap tests, which require trained practitioners to evaluate cellular changes. In the U.S., however, the advantages in real-life practice remain to be determined.
And, in fact, improper use of the test is widespread. The July study, which was a survey of 592 healthcare providers across the nation who routinely use Pap tests, found that about 75% had used the HPV test and 28% of those reported using the low-risk HPV test. About 60% of providers reported that they test women under the age of 30.
There are reasons why improper use occurs. For one thing, Karam said, guidelines from different organizations vary, which can be confusing for practitioners. For another, patients can be frightened by a positive HPV test and ask to get tested again.
One thing is clear: Screening has cut the rate of cervical cancer by half in the last 30 years, and most cases today occur in women who have never been screened or have not been screened in five years. As long as the tests are used appropriately, “it’s not as important which test you get as long as you get one of them,” Saslow said.
