Related topics: •  Cervical Cancer •  Tests & Procedures

A Pap smear is a test used to detect cells that might develop into cancer of the cervix, the part of the uterus that connects to the vagina. The test also turns up infections and other abnormal cervical cells. Since its introduction in the 1940s by George Papanicolaou (for whom it's named), the Pap smear has become the most successful cancer screening tool ever invented. This simple test has cut cancer deaths among women by 70 percent.

You should have Pap smears routinely beginning about three years after you become sexually active or at the age of 21, whichever comes first. The US Preventive Services Task Force recommends screening at least every three years. However, the American Cancer Society recommends screening every one to two years for women under the age of 30, and every two to three years for those over 30 who have had three normal pap test results in a row. If you meet any of the following criteria, you should have an annual Pap smear:

•You're HIV-positive.

•You were exposes to diethylstilbestrol (DES) before birth

•Your immune system is below par (as a result of recent transplant surgery, for example).

•You have had abnormal Pap smears that showed precancerous cells

•You've had cervical, uterine, vaginal, or vulvar cancer.

There's no hard-and-fast requirement that you be tested, but a Pap smear is a precaution that saves the lives of thousands of women in the United States each year. Insurance companies often pay for it as a standard part of an annual pelvic exam. If you don't have insurance, or if your insurance covers only one test every three years and you feel you need one more often, call a local women's clinic or a city health clinic. Many offer Pap smears for free.

It's best to have one when you're not menstruating. Don't douche and don't use a spermicide or any vaginal medication or lubrication for two or three days before the test.

It's very simple. The doctor or nurse will ask you to lie on your back and place your feet in foot stirrups, which are often padded for comfort. Next he or she will use an instrument called a speculum to push the walls of your vagina slightly apart and hold them open during the exam (many doctors now warm their speculums so they won't feel cold to the touch). Using a tiny brush or spatula, he or she will remove some cells from the surface of your cervix. This sample is smeared onto a glass slide, sprayed with a fixing chemical, and sent to a laboratory for examination.

Trained lab workers put your sample under a microscope and examine it for abnormal cells. Then they give it a classification and return it to your doctor, who contacts you to let you know the results. These are generally available within 10 to 14 days. Some physicians get in touch only if an abnormality shows up, but if you don't hear from your doctor, call and ask for your results. That way a suspicious finding won't go unnoticed.

Doctors have classified Pap smears differently over the years, causing much confusion. Today, most labs in the US use the Bethesda System to classify Pap test results. The Bethesda System classifies tests with no abnormalities as “negative for intraepithelial lesion or malignancy”. Tests that show some abnormality are classified in one of the following ways:

•Abnormal: Some abnormalities were found. Your doctors may recommend follow-up tests.

•ASC (Atypical squamous cell). Squamous cells are on the surface of the cervix. This classification means that the cells are not completely normal, but doctors are unsure what the cell changes mean. ASC-US usually refers to mild abnormalities that are sometimes related to the human papilomavirus (HPV). ASC-H may reflect a higher risk of being precancerous.

•AGC (Atypical glandular cell)). AGC means that there were some abnormalities in your glandular cells, which are found in the lining of the cervix.

•LSIL (Low-grade squamous intraepithelial lesion). This is considered a mild abnormality caused by HPV infection and is usually not precancerous.

•Precancerous: If your results are precancerous, it is very important that you get the recommended tests and treatments.

•HSIL (High-grade squamous intraepithelial lesion). These are more severe abnormalities that have a higher likelihood of progressing to invasive cancer.

•AIS (Adenocarcinoma in situ). AIS means that precancerous cells were found in the glandular tissue.

•Cancerous: Cancer cells are found in the cervix. In this case you will likely be referred to a gynecological oncologist.

All screening tools carry the possibility of error, and Pap smears are no exception. Sometimes a lab may classify a Pap smear as normal even if it contains abnormal cells (this is known as a false negative) or as abnormal even when the cervix is perfectly okay (this is known as a false positive). Both are rare; fewer than 1 percent of Pap smears turn out to be false negatives. Annual gynecological exams that include Pap smears are the best way to guard against a false negative.

Don't panic. Even though it can be frightening to hear that your Pap smear has been judged abnormal, you're not likely to have cancer. An abnormal result usually means that there's a minor problem with the cervix, one that may not even need treatment. You'll probably be asked to go back for either a second Pap smear or further exams. Sometimes a smear is classified as abnormal only because the lab worker had problems reading the sample.

If your Pap-smear results show that a few cells are abnormal, you have what's known as mild cervical dysplasia, which is considered a precancerous condition. ("Plasia" means growth, and the term "dysplasia" means that some cells aren't growing normally.) This is easy to treat, and cancer can almost always be prevented. In severe dysplasia, part of the cervix's surface is covered with abnormal cells - but only the surface. This form of dysplasia will need to be dealt with immediately so that it doesn't develop into cancer.

In any event, an abnormal Pap-smear doesn't have to be bad news. In fact, British researchers analyzed the medical records of almost 350,000 women over 20 years and found that at least 80 percent of those with abnormal cervical cells never went on to develop cancer. In the rare cases in which invasive cancer is found, there are a variety of treatment options, including radiation.

-- Kate Lee is a former associate editor at Consumer Health Interactive and researcher at Time Inc. Health. She is currently a senior editor at BabyCenter.

References

Last updated September 23, 2009
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