Will Pap smears soon be history? What we know about shift to HPV tests

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Provinces have begun rolling out a test for high-risk strains of human papillomavirus (HPV) that will soon replace the Pap test for routine cervical cancer screening in Canada. It won’t get rid of the idea of a “gyne” exam forever, said Dr. Amanda Selk, an obstetrician-gynecologist at Toronto’s Women’s College Hospital. “Some people think that, ‘Oh, my god, I’ll never need a Pap again.’ It’s not quite true,” she said, for reasons we’ll get into. But there is talk about Paps eventually disappearing. HPV testing is better at detecting pre-cancerous lesions or cancer than the Pap (Papanicolaou) test, with longer intervals between tests and the possible option of do-it-yourself testing at home. But the shift from Pap to HPV testing will require a major overhaul of cervical screening programs, as well as ample public education “to overcome natural resistance to change” and ensure a smooth and controversy-free transition, Selk and her co-author, Dr. Emily Delpero, wrote in a commentary published last year. The National Post’s Sharon Kirkey spoke with Selk about the shift. Here are some key takeaways.

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Why the move from Pap smears to testing for HPV?

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Pap smears have been used to screen for cervical cancer for more than half a century. However, while a Pap can detect abnormal cells in the cervix, HPV testing gets at the root source by looking for the DNA of cancer-causing strains of HPV, the most common sexually-transmitted infection. An HPV test can identify women at risk before any abnormal changes occur.

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HPV testing has replaced Pap tests in Prince Edward Island. Quebec is slowly rolling out HPV testing, Ontario is working on a “multi-year” transition to include HPV testing in its cervical screening program and British Columbia is expected to announce an “updated cervix screening test” in early 2024.

After years of stagnating rates, cervical cancer is now the fastest increasing cancer among females, according to the latest Canadian Cancer Society statistics. It’s not clear why, but the pandemic had a major impact on cervical screening and follow-ups of abnormal results. About 1,550 women are expected to be diagnosed with cervical cancer this year.

The disease is almost exclusively caused by HPV, according to the Canadian Partnership Against Cancer, which has a goal of eliminating cervical cancer by 2040. There are two main types of HPV cervical cancer: squamous and glandular cancers. Glandular cancers are usually caused by HPV type 18 — and glandular precancers are not well picked up on Paps, Selk said. “It’s sort of a lucky thing when you do pick them up (via a Pap).”

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Screening with a Pap, in fact, misses almost half of existing abnormalities, Selk and Delpero wrote in the CMAJ. More frequent screening — every two to three years, depending on the province — can “mitigate harms” by catching abnormalities missed in previous screens.

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HPV testing is more sensitive. Unlike a Pap, which requires a specialist in cell pathology to detect precancerous cells from a sample of cells scraped from the cervix, HPV testing uses polymerase chain reaction, or PCR, which amplifies small segments of DNA. HPV detects 95 per cent of abnormalities and is more reliable than a Pap smear. “When Paps are negative, they miss more stuff,” Selk said. If an HPV test is negative, “you’re very unlikely to get into trouble, and if it’s positive, the virus is there.

“It doesn’t mean you’re going to get cancer,” Selk said. “But it does mean you have a risk, so now we have to look more carefully” via a traditional Pap test or colposcopy, “where we actually look at your cervix,” said Selk, a past president of the Canadian Society of Colposcopists.

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“So, if you do have HPV, you will still need to go that second step (with a Pap and/or colposcopy) if you want to try to figure out what’s going on.”

The other advantage of HPV testing for a country in the grips of a primary care access crisis is that women can use home kits to collect their own samples.

How is the DIY test done, and is it as accurate as having a doctor do it?

“That was a question originally: if it’s a patient self-sampling from the vagina (as opposed to the cervix, like a Pap) is it as good?” said Selk. The cervix and vagina “have pretty close concordance, meaning they’re almost the same.”

The self-testing kits use a conical-shaped brush similar to a Q-tip that’s inserted into the vagina then placed immediately into a collection tube and mailed to a lab for testing.

“Self-sampling” is generally as accurate as samples collected by a doctor or nurse using a speculum, it allows women to take the test in the privacy and comfort of their own homes and could boost participation rates in cervical cancer screening programs, according to Canada’s Drug and Health Technology Agency. B.C. and Alberta have pilot tested home HPV testing.

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Why stretch the testing intervals out from every two or three years for a Pap, to every five years for an HPV test?

“Because it works more on how high your risk is,” Selk said. “If you’re HPV negative and you have a normal immune system, we can spread the interval out to five years because, in order to develop a cancer, generally speaking, you need to both acquire the virus and have it stay there for a while before we see any trouble.”

More frequent testing is stressful. “We used to do Paps every year, and we used to over-treat things,” she said. “But when you leave people alone their body often clears things, and they get better.”

“We only really need to watch more carefully people who have persistent HPV positive disease, or if you have specific strains of HPV that are higher risk.”

Again, a Pap can help “triage” those with positive HPV tests, to determine who needs to be seen first for a colposcopy, she said. “So, the Pap will not be gone for a while, but the hope is eventually it will go.”

Dr. Amanda Selk, of Women’s College Hospital in Toronto: “At the end of the day, you don’t want to get into treating cancer — you want to prevent cancer.” Photo by Women’s College Hospital

It’s all a little complicated, which is the biggest problem with all of this, Selk said. Australia’s rollout was met with widespread suspicion. A nationwide petition garnered over 70,000 signatures over suggestions it was purely a cost-saving move. Doctors began screening earlier, and more often than recommended, “either owing to patient demand or provider judgment, possibly in part a result of lack of trust in the new paradigm,” Selk and Delpero wrote.

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“It’s new to the public,” Selk said. “It’s new to physicians. It takes time when we have changes, and this is not a simple change. It’s actually complicated algorithms. It’s why we need lots of education.”

Since 2014, the Canadian Task Force on Preventive Health Care has recommended Paps every three years between ages 25 to 69. Some provinces adopted the changes, some haven’t and still recommend Pap testing starting at age 21. However,  Selk said there isn’t good evidence that screening programs prevent cancer in those under age 25.

Shouldn’t cervical cancer rates be declining as more kids are vaccinated against HPV?

The Canadian Paediatric Society recommends routine HPV vaccination for girls and boys between the ages of nine and 13. HPV vaccination before age 17 leads to a 90 per cent reduction in invasive cervical cancer risk.

All provinces and territories have publicly funded, school-based HPV vaccination programs, “but we originally didn’t have them everywhere, and we originally vaccinated only girls,” Selk said.

The school programs also aren’t all that old, launching between 2007 and 2010, “and they don’t have perfect uptake,” she added.

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Why might there be resistance to the HPV vaccine?

“It may depend on how they’re promoted in one area, how people feel, how easy it is to get them,” Selk said. During the pandemic, when school-based programs were temporarily shelved, “I had kids that age that needed (an HPV vaccine), and I know everything about this, and I found it extremely hard to get them their vaccines. I can’t imagine most people going to that effort.”

Caught early, cervical cancer can be successfully treated. “But at the end of the day, you don’t want to get into treating cancer — you want to prevent cancer,” Selk said.

“There are two ways to prevent cervical cancer: vaccines, so you get rid of getting the virus in the first place, and screening with HPV.”

The increase in rates for the first time in many years is “sad and problematic,” Selk said.

“It’s a cancer we can truly prevent for most people.”

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