Pap test guidelines for cervical cancer screening

A Pap test is a screening test for cervical cancer. It can detect early, precancerous changes to the cells of the cervix. These precancerous changes are caused by the human papillomavirus (HPV), which is spread through sexual contact.

Regular Pap screening is a crucial defence against cervical cancer. Cancer Care Ontario guidelines advise women in Ontario who are, or have ever been, sexually active to have a Pap test every three years from age 21 through 70. After age 70, women who have had three normal Pap tests in the preceding 10 years can stop screening.

Cancer Care Ontario Pap test guidelines at a glance:

• under age 21: no testing
• ages 21-70: Pap test every three years
• over age 70: no further testing if she has had three normal Paps in the preceding 10 years

Unlike other types of cancer screening, Pap testing can actually prevent cancer. Other tests, such as mammography, can identify early-stage cancers, but Pap testing can identify potential cancer cases before they develop.

“We pick up changes that may be more likely to progress to cancer, and treat them before they do,” says Dr. Sheila Dunn, research director at the Family Practice Health Centre at Women’s College Hospital. “So it’s prevention that we’re talking about.”

The HPV link

Because HPV, the virus that causes cervical cancer, is spread by sexual contact, women who have never been sexually active do not need screening. However, the definition of sexual activity is very broad. Sexual activity includes not only intercourse, but also oral sex and genital touching with hands or fingers with a partner of any gender.

Women under 21 are not screened, regardless of their sexual history.

“That’s really important because changes on Pap smears are very frequent as women become sexually active and they get infected with HPV,” says Dr. Dunn.

However, in most of those young women, the infection will clear on its own. But until it clears, those women may show HPV-related changes on their Pap tests, which can lead to unnecessary treatment.

“Finding an abnormal Pap smear in a very young woman often will take her down the path of having colposcopy and possibly treatment with excision of areas of the cervix or laser treatment, and we now know that not only is that not necessary in almost all cases – particularly in very young women – but it also has implications in terms of negative outcomes for pregnancy such as preterm labour,” Dr. Dunn explains. “It’s not a totally benign treatment.”

The goal of the screening guidelines is to prevent unnecessary treatment while still identifying women who do need treatment. Research has shown that there is no benefit to screening women under age 21.

Lifelong screening

Pap tests are recommended for all women who have ever been sexually active, regardless of their current relationship status.

“It’s often surprising for women who have been in longstanding monogamous relationships when their Pap test comes back abnormal,” Dr. Dunn says. “And yes, you do need screening even if you haven’t been sexually active in 20 years: if you were sexually active 20 years ago, you still need to be screened.

“We really want to promote life-long screening,” she adds. “It’s often as women get older that we’re identifying these persistent HPV infections that are causing the precancerous changes.”