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HPV test better at detecting cancer than a Pap smear

05 July 2018

Nearly each type of cervical cancers is caused due to the infection by one of the 12 types of oncogenic human papilloma viruses (HPV). Almost all cervical cancer cases are linked to HPV infection, and HPV testing detected pre-cancers earlier and more accurately than the Pap test among the 19,000 women in the Canadian study.

Of note, the Canadian Task Force on Preventative Health Care differs from the USA task force - it recommends Pap smear screening every three years between ages 30 and 69, citing weak evidence for screening women ages 25 to 29. Pap smears will still be recommended for women under 30, since HPV is so common that many in that age range would test positive for an infection that will end up resolving on its own.

According to NPR, The American Cancer Society claims almost 13,000 women in the US are diagnosed with cervical cancer annually and more than 4,000 women die from it even when they have access to regular screening and treatment.

In an accompanying editorial, L. Stewart Massad, MD, of the Washington University School of Medicine in St. Louis, argued that cytology testing does not significantly improve the accuracy of HPV testing, but it does increase costs and false-positive results.

Dr. Gina Suzanne Ogilvie of the Women's Hospital and Health Center in Vancouver and colleagues set up a comparison study.

Pap smears involve scraping cells from the cervix and examining them for cancerous changes, also known as "cytology" testing.

The authors stated that one of the concerns related to primary HPV screening is lower CIN2+ specificity, "leading to higher screen positive rates and the resulting need for more colposcopies and biopsies". However, other experts now say the Pap smear should be dropped in favor of regular HPV testing.

According to the American College of Obstetricians and Gynecologists, women aged 21 to 29 should have a Pap test alone every three years. Previous research has indicated that HPV testing alone or combined with a Pap smear is linked to increased detection of precancerous lesions in the first screening round, followed by a subsequent reduction in precancerous lesions.

The Pap test identifies abnormalities in cervical cells, flagging health-care providers to take a closer look to see if they are precancerous, and then take appropriate action. "This has been building for decades", he said, adding that the Pap smear is "crude and inaccurate" while the HPV test is much more precise, operates on the molecular level and can provide information on the specific type of HPV causing the problem.

The study is titled "Effect of Screening With Primary Cervical HPV Testing vs Cytology Testing on High-grade Cervical Intraepithelial Neoplasia at 48 Months - The HPV FOCAL Randomized Clinical Trial". Both group were tested again using both methods after four years.

"This is one study", he said.

For women under 25, the Pap test is still the standard because many young women are infected with HPV, Ogilvie said. Additionally, they could not be diagnosed with invasive cervical cancer or have received a total hysterectomy. "The ASCCP [American Society for Colposcopy and Cervical Pathology] pointed out that just doing the HPV testing would miss some people, and so they advocated for co-testing". This new study could prove important in deciding on practice guidelines.

Most cervical cancers are caused by a particular strains of the Human papillomavirus, or HPV. From the participants, 9,552 women were screened using HPV test and those who were negative for the test came back after four years for a check if they had a pre-cancerous or cancerous lesion.

Medical students learn how to insert a speculum, part of the process of performing a Pap smear.

At present, the NHS screening programme for cervical cancer starts with a smear test. Women whose smear test results show possible low-grade or borderline changes to cells will have the sample tested for HPV.

HPV test better at detecting cancer than a Pap smear