HPV vs. Pap test? Why some provinces are making the change for cervical screening

As more provinces move towards Human papillomavirus (HPV) tests for cervical screening, most recently Ontario, questions about why an HPV test would be better utilized over the current procedure, a Pap test, are being asked.

The Canadian Cancer Society provides information on both Pap tests and HPV tests and answers some frequently asked questions for those wondering.

What is an HPV test?

An HPV tests looks at a small sample of cells that have been collected and tests then for DNA or mRNA of high-risk types of HPV.

HPV is group of more than 100 different types of related virus and spreads through intimate skin-to-skin contact during sexual activity. Currently there is no treatment and it can cause abnormal changes to cells in mouth, throat, cervix, vagina, vulva, penis or anus.

Infection with high-risk strains of the HPV is a known prerequisite for developing cervical cancer.

How is an HPV test preformed?

HPV testing is done by taking a sample during a Pap test. It can also be done on a separate sample, but it will be collected in the same way as a Pap test.

To collect a sample, a doctor or nurse places a speculum, a clear plastic or metal device, in the vagina.

The doctor or nurse uses a small brush (called a cytobrush or cytobroom) to gently collect cells from the cervix, which leads into the uterus.

After collecting the cells, the doctor or nurse puts them into a container. The sample is sent to a lab where it is tested to see if it contains the DNA or mRNA of high-risk types of HPV.

How does it differ than a Pap test?

While an HPV test is conducted during a Pap test, the difference is that a Pap test uses cytology-based screening to detect precancerous cervical cells while HPV tests uses a PCR testing of cervical samples.

Also, a follow-up to a Pap test if the cells are abnormal usually includes an HPV test.

“An HPV test is really focused on figuring out whether the virus that is the precursor to all of the problems, whether it’s there. A PAP test, which is what we’re all used to seeing and doing, is where we are looking at abnormal cells on the cervix,” explained Dr. Lynn Sterling, an OB-GYN at Humber River Hospital.

Why are provinces making the switch?

Pap testing has a low sensitivity at just 55.4 per cent, which means that screening misses almost half of existing abnormalities. HPV PCR tests have a higher sensitivity than cytology-based screening at 94.6 per cent.

“HPV testing is going be much more effective and allow us to better do our jobs. We’re going be able to pick up cervical cancer more effectively. We’re going to be able to figure out who’s at higher risk based on what strains of the virus they have,” said Dr. Sterling.

Dr. Sterling said it also changes the frequency of how often you need the test.

“Right now, we’re doing routine Pap testing for most patients every three years if they’re lower risk whereas the HPV test is very sensitive, meaning it’s much better able to detect if you are someone that’s higher risk and so we’re going to be spacing it out to every five years.”