What Is The Difference Between Pap Smears and HPV Testing?
There isn't a big difference between pap smears and HPV testing in terms of their purpose. Both tests examine cells taken from the cervix to test for cervical cancer.
According to the World Health Organization, cervical cancer is the second most common cause of death by cancer in women globally. A recent study reports that HPV testing is more effective in identifying precancerous cells than longer established Papanicolaou smear test. The study which was carried out in Canada and is now published in the The Journal of the American Medical Association reports that co-testing cervical cancer using pap smears and HPV testing may no longer be necessary.
- Cervical cancer is the fourth most common cancer amongst women in the U.S.
- The American Cancer Society predicts that there will be 13,240 cases of invasive cervical cancer in 2018. It is predicted 4,170 women will die by cause of cervical cancer.
- Cervical cancer is most commonly diagnosed in women between the age of 35 and 44.
- HPV infection is the the cause of 99% of cervical cancers.
- It is estimated that 50% of of women will be infected with the HPV virus at some point in their lives, however not all cases of HPV infections are cancerous.
- The interval between contracting HPV and the development of cervical cancer can be upto 15 years.
- How do pap smears and a HPV tests differ?
- What is HPV?
- Research on the differences in pap smears and HPV testing
- What is the future for cervical cancer screening?
How do pap smears and a HPV tests differ?
Pap smears and HPV tests share the common goal of identifying precancerous or cancerous cells on the cervix, which are indicative of cervical cancer. The cervix is the entry to the womb.
Medical professionals test for cancerous cells by scraping a sample from the cervix. The difference in pap smears and HPV testing lies in what is being examined from the collection of cells.
In the case of a pap smear, the collected sample is examined under a microscope to identify high-risk abnormal cells that could potentially develop into cervical cancer. In HPV testing, collected samples are examined for cancerous strains HPV-16 and HPV-18 which cause cervical cancer.
HPV infected cells can be found on the throat, mouth, anus, tip of the penis, the vagina, vulva and as aforementioned, the cervix.
The study which was funded by the Canadian Institutes of Health Research found that women who had a negative result following their HPV test had half the risk of of developing cancer vs. the women who had received a pap smear, the result was similar for women who had had a “co-test”, an instance in which the sample received a HPV test as well as a pap smear.
In another study carried out in 2014, it was found that women who don’t show signs of the HPV virus are less likely to develop cervical cancer than women who receive a negative pap test. This reinforces the idea that HPV is the most common cause of cervical cancer.
What is HPV?
Human papillomavirus or HPV is a group of 150 viruses which can be contracted through intimate skin to skin contact.
HPV is the most common sexually transmitted disease in the world, it is possible to become infected through vaginal, anal or oral sex.
Varying strains of HPV have varying outcomes. Some strains are responsible for genital warts while others can cause cancer of the cervix, vulva, vagina, penis, anus or in cases of oral transmission, the cancer can develop at the back of the throat, the tongue and the tonsils.
The HPV Information Centre reports that there are 600 million cases of HPV globally.
According to the Centers for Disease Control, 80 million people are currently infected with HPV, however the majority of these cases will not develop into cervical cancer as the body can fend off the virus independently.
Research on the differences in pap smears and HPV testing
The study involved 19,009 females in British Columbia, Canada. The data collection took place between 2008 and 2014, examining women aged between 25 and 65. The sample groups were divided into two groups. One group underwent HPV testing alone. In the other sample group, women were enrolled to undergo cytology-based pap smears. If women in the HPV testing group received positive results, it was followed with a pap smear. Women who had negative results for HPV underwent a cytology-based pap smear during the two years following their result.
The study shows that a larger proportion of women presented pre cancer cells in the first round of HPV testing compared with results from the pap smear. There was also a higher rate of follow up appointments in those that had received a HPV examination as opposed to those who had received a pap smear. During the two year investigation, the number of referral rates amongst those who had taken a HPV test versus those who had undergone a pap smear was significantly lower while the referral rates for those who had gone for a pap smear had rose.
What is the future for cervical cancer screening?
The U.S Preventive Services Task Force (USPSTF) recommends that women between the age of 21 and 29 years undergo cervical cytology screening every three years. The USPSTF recommends that cervical cytology screening every three years or high-risk hrHPV testing every five years in women who are considered high risk. Women are considered to be at a higher risk of contracting cervical cancer between the ages of 30 -65 years.
The study suggests that HPV testing may be the only necessary method for cervical screening moving forward. It concluded that “use of primary HPV testing compared with cytology testing resulted in a significantly lower likelihood of CIN3+ at 48 months. Further research is needed to understand long-term clinical outcomes as well as cost-effectiveness.”
It has been proven that 99% of cervical cancer cases are by cause of HPV, which would indicate that while both tests may be equally useful within their own rights, prioritizing regular HPV screening is necessary moving forward.
Written by Hannah Kingston | Approved by Medical Director Dominic Rowley