HPV test is more effective and as safe as Pap smear in cervical cancer screening

A study conducted by HUS and the Finnish Cancer Registry shows that HPV screening is a more effective method and as safe as a traditional Pap smear, i.e. cytological screening, in the prevention of cervical cancer.

The HPV test and the Pap smear are both cell samples from the cervix. Both are collected in the same way in a gynecological examination either in a laboratory, or during a public health nurse’s or doctor’s appointment. The Pap smear reveals cell changes that have already occurred. The HPV test is used to look for HPV, or papillomavirus, which may later cause cell changes.

In other words, the HPV test detects precancers earlier and may therefore make longer screening intervals possible in future. The study strengthens the current understanding that HPV screening works better than Pap screening.

In the study, HPV-based and cytological screening were compared during two screening rounds in Finland’s national screening programme between 2012 and 2022. In other words, an HPV sample was taken from each patient in the study at two different time points. The data comprised over 1.1 million women and a total of 1.57 million screenings. The follow-up data extended to October 2024.

HPV test detects changes earlier than Pap smear

In HPV screening, precancers were found in 0.92 per cent and in Pap screening, in 0.35 per cent of the women screened. Of those who had an HPV test in the screening, 3.37 per cent were referred to a colposcopy, i.e. an endoscopy of the cervix, and 0.98 per cent of those who had a Pap smear. In the second screening round, precursor findings decreased by 60 percentage points in those who had an HPV test, whereas the decrease was only 6 percentage points in those who had a Pap smear.

HPV and Pap screenings have been introduced at different times in different parts of Finland. As a result, there were some differences between those who had an HPV test and those who had a Pap smear in terms of the background variables. The researchers also examined the findings by standardizing those who participated in the screening in terms of age, the year of screening, education and the region.

Considering the background variables, the findings remained similar: the number of colposcopy referrals among women who had an HPV test was three times and the number of precursors detected 2.2 times as high as among those who had a Pap smear. If the first HPV test was negative, precancers were found in only 0.2 per cent of the women in the second screening round 5 years later.

“The result indicates that the HPV test detects precancers well, including those that would have been missed in Pap screening. A negative HPV test is also more reliable than a negative Pap test,” says Doctoral Researcher, Specializing Physician Iiris Turunen.

A negative HPV result may extend the screening interval safely

In women with a negative result, the risk remains very low for at least five years. For this reason, it may make sense to extend the screening interval in the future, especially for those over the age of 50.

”The result indicates that the HPV screening is working. Especially after a negative test, there is no need to collect additional samples between the mass screenings. A Pap smear should probably no longer be taken from anyone as the primary screening test”, says Docent, Ilkka Kalliala, a Clinical Teacher.

There has been a significant increase in the number of colposcopy referrals as a result of HPV screening.

“Because different HPV genotypes have a different risk of developing into cancer, the increased number of referrals could in the future be reduced by introducing a more accurate HPV test, which will also produce information about different HPV genotypes. Women who have been diagnosed with an HPV type with a lower risk of cancer could therefore be monitored safely for a longer period of time before referring them to a colposcopy and avoid unnecessary further examinations,” says Development Manager Veli-Matti Partanen from the Finnish Cancer Registry.

In addition, the second HPV screening round revealed that the number of colposcopy referrals had begun to decrease. This indicates that even precursors that had not been detected in the Pap smear are caught in the early stage of HPV screening.

“When HPV screening becomes established practice, the number of colposcopies could be expected to gradually start to decline even just for this reason,” Turunen says.

The study is based on data from the Finnish Mass Screening Registry and covers the population-based screening programme in the whole country.

Cervical cancer is the fourth most common cancer in women worldwide. Cancer develops slowly through precursors. Its single most important background factor is a prolonged papillomavirus (HPV) infection.

Women aged 25–65 years are invited to screening for cervical cancer free of charge every five years. For women aged 30 years and over, screening is based on an HPV test. For women under the age of 30, screening is based on a Pap smear.