What is a pap smear and when should women start getting them?

A pap smear is a cell sample from the tip of the cervix that is examined by a pathologist for evidence of cervical cancer or pre-cancer cells. The medical name for pre-cancer cells is dysplasia and this is divided into mild, moderate or severe changes or CIN I, II or III.

There are about 15,000 new cases of cervical cancer diagnosed in the United States per year but many hundreds of thousands of pap smears are obtained showing some degree of dysplasia. Almost all dysplasia and cervical cancer is caused by human papillomavirus or HPV. This is a highly contagious, sexually transmitted virus that can infect the cervix and over a period of time (usually 10-15 years) induce cervical cancer changes. This occurs in a progression from mild to moderate to severe dysplasia, then microscopic cancer, then actual invasive cervical cancer.

There are over 100 genotypes of HPV viruses. Genotypes 16 & 18 are the usual culprits but there are a dozen others. This group is called high-risk HPV. All the others are called low-risk and they never cause cervical cancer. Most HPV cervical infections resolve spontaneously thanks to the body’s immune system. There is no treatment otherwise. 95% of HPV infections will go away but this may take 6 – 18 months.

Several million HPV infections occur in the United States each year. The male partner usually has no symptoms and doesn’t seek medical attention or develop any complications from his HPV infection. If the high-risk HPV persists over 2 or 3 years, it can lead to pre cancer and cancer changes but remember that 95% of all HPV infections resolve or disappear on their own over 6-18 months.

Given the above set of facts, the American College of Obstetrics and Gynecology has recommended that no woman under 21 years old receive a routine annual pap smear. If pap smears are taken in this age group a significant percent will show pre-cancer changes induced by the HPV virus that would disappear when the virus disappears. In the past these patients would have been subjected to diagnostic procedures (colposcopy, biopsy, loop electrosurgical excision procedure) for abnormal cell changes on the pap smear that would have resolved on their own or would not have had enough time to cause a serious problem by age 21.

All of the national agencies (eg. American Cancer Society, etc) have not made this same recommendation but I suppose they will in time. Some patient histories would mitigate for an examination and pap smear depending on their circumstances. There is a vaccine available that protects against getting genotypes 16 and 18 HPV infection. This vaccine is FDA approved for females aged 12-26. There is no reason males shouldn’t receive it as well but it is not FDA approved for this group. The vaccine is much more effective if the woman has never had any HPV infection. Therefore women should be vaccinated as early as possible, at age 12 or before they might become sexually active. If vaccinated they reduce their risk of ever getting cervical cancer by 80%. But even if vaccinated they should begin yearly pap smears at age 21. All sexually active women under the age of 25 should be screened yearly for chlamydia and gonorrhea but this can be done with a urine specimen. Contraception can therefore be prescribed without a pelvic exam.