Cervical cancer: What are the benefits of HPV tests for cervical screening?

Cervical cancer doesn't cause any symptoms at first, or only very few, so it is often not detected for a long time. If women have symptoms such as frequent vaginal bleeding between periods, the cancer might already be quite advanced. The goal of screening tests is to detect cell changes (dysplasia) early enough for them to be treated successfully before cancer has a chance to develop.

Pap tests (also called smear tests) have been used to screen for cervical cancer in Germany since the 1970s. This test involves examining cells on the cervix to detect any changes. In Germany, statutory health insurers pay for women between the ages of 20 and 34 to have a smear test once a year. From the age of 35, women are offered a combined test that includes a smear test and a test for certain human papillomaviruses (an HPV test) every three years.

The HPV test can be done to find out whether a woman has an HPV infection and is therefore at greater risk of cervical cancer. But the HPV test can't detect abnormal cell changes. For this reason, if the HPV test shows that a woman has an HPV infection, she will have to have a Pap test and perhaps other tests too.

Several large studies have compared HPV tests with Pap tests to see what advantages they have in cervical screening. The studies looked into whether HPV tests are better at detecting high-grade dysplasia (abnormal cells that have changed a lot) and preventing cervical cancer. A total of more than 235,000 women participated in the six studies. HPV tests were used in very different ways in these studies. For example, sometimes they were used instead of Pap tests, and sometimes they were used in addition to Pap tests. In the studies, both of the tests were carried out every three to five years. This is different to the situation in Germany, where Pap tests are offered once a year.

The results of these studies show that HPV tests are more effective than Pap tests at discovering high-grade dysplasia (abnormal cells that are likely to turn into cancer). Individual Pap tests fail to detect half of all cases of dysplasia. HPV tests help to detect a lot more cases.

If Pap tests and HPV tests are carried out regularly over a long time period, both detect most areas of abnormal cells. But HPV tests were slightly more effective overall: Fewer women who had HPV tests developed cervical cancer. The studies lasted about five years. This is what was found during that time:

• About 4 out of 10,000 women developed cervical cancer if they only had Pap tests.
• About 1 out of 10,000 women who had HPV tests (in addition to, or instead of, Pap tests) developed cervical cancer.

But the studies didn't allow any conclusions to be drawn about whether women who had an HPV test were less likely to die of cervical cancer.

HPV tests can also have disadvantages. Many abnormal cells don't develop into cervical cancer. This means that, compared to Pap tests, HPV tests might also be more likely to detect abnormal cells that would never have developed into cancer. This kind of diagnosis is of no benefit to women and might mean that they end up having unnecessary treatment, such as surgery to remove tissue from the cervix (conization). Abnormal cells usually return to normal on their own, especially in women under the age of 30.