Until the Pap test was widely adopted in the United States in the late 1940s, cervical cancer was the number one cause of cancer death in women. After the widespread use of the Pap test, however, cervical cancer cases dropped by 70 percent. This is a huge success story.
(By the way, cervical cancer remains the number two cause of death worldwide -- and in very poor countries it tops the list of deadly cancers, as many countries cannot afford the costs associated with Pap tests.)
By 1999, the World Health Organization concluded that there was a single cause of cervical cancer -- the human papillomavirus. HPV is a simple double strand of DNA enclosed in a protein capsule that resembles a soccer ball when viewed under a special microscope. Although there are over 100 types of HPV, only about 15 types are linked to cancer. These 15 types are commonly called "high-risk strains" of the virus.
Soon after the discovery of HPV as the cause of cervical cancer, a DNA test to look for the high-risk strains of HPV was developed. This simple test is done using the same scraping of cells used for the Pap test. Although most women are exposed to HPV at some point in their lives -- which is why we suggest that all women undergo cervical cancer screening -- most women will fight off the virus within a year or two, and the virus either disappears altogether or remains dormant. Only about 5 percent of women will not fight off the virus, and these women will continue to test positive with the HPV test and may eventually develop precancerous cell changes -- and even cancer -- if these cell changes aren't treated.
The Pap test looks for cell changes under the microscope caused by the virus and is not foolproof. On occasion, the cell changes are not discovered and cervical cancer is eventually discovered. One of my sisters was diagnosed with cervical cancer earlier this year despite previously normal Pap tests. On the other hand, there are other causes of a mildly abnormal Pap test besides HPV, such as low estrogen in women after menopause. I had an abnormal Pap test after menopause which was from low estrogen and not from HPV.
Here is a quick review of what I would recommend:
All young girls and women should begin an every other year Pap test, starting at age 21.
Any inconclusive or mildly abnormal Pap test result should lead automatically to an HPV test. Women who have a mildly abnormal Pap test and also test positive for high-risk HPV need more testing, such as a colposcopy and closer follow up. Women who don't have high-risk strains of the virus and, therefore, test negative with an HPV test can simply have their Pap test repeated in 6-12 months.
Starting at age 30, women who have had three consecutively normal Pap tests can have a Pap test every three years (they can ask to have an HPV test at the same time as their Pap test). If they have a normal Pap test and no high-risk strains of HPV, they can safely have a repeat check for cervical cancer every three years. It takes about three years from the time a woman is exposed to HPV to develop serious cell changes that can be detected with the Pap test. That doesn't get women off the hook for the all-important regular checkup, including a pelvic exam, however.
Women who have had a hysterectomy and their cervix removed for benign conditions, such as fibroids or heavy bleeding, can stop having Pap tests altogether.