You will be asked to lie on your back with your feet in the stirrups. A pelvic examination will be done, and a speculum (an instrument used to open the walls of the vaginal canal in order to examine the interior) will be inserted into your vagina and opened slightly.

A sample of cells from the outside and the canal of the cervix is taken by gently scraping the outside of the cervix with a wooden or plastic spatula, then inserting a small brush that looks like a pipe cleaner into the canal.

The cells are placed on a glass slide and sprayed with a fixative, or put in a bottle containing a preservative, then sent to the lab for examination.

The Pap test is used to detect abnormal growth of cervical cells at an early stage so that treatment can be started when the condition is easiest to treat. This microscopic analysis of cells can detect cervical cancer, "precancerous" changes, inflammation (called vaginitis), infections, and some sexually transmitted diseases (STDs). The Pap test can occasionally detect endometrial (uterine) cancer or ovarian cancer, although it was not designed for this purpose.

Women should begin to have Pap tests at the age of 18 years or whenever they start having sex. Young people are more likely to have multiple sex partners, which increases their risk of certain diseases that can cause cancer, such as human papillomavirus (HPV). Doctors have varying opinions about how often a woman should have a Pap test. The American Cancer Society recommends that a Pap test be done annually for two consecutive negative examinations, then repeated once every three years until age 65 for women without symptoms of gynecologic problems. Many other doctors, however, recommend annual Pap tests for all their patients.

Women with certain risk factors should always have yearly tests. Those at highest risk for cervical cancer are women who started having sex before age 18, those with many sex partners (especially if they did not use condoms, which protect against STDs), those who have had STDs such as genital herpes or genital warts, and those who smoke. Women older than 40 also should have the test yearly, especially in the event of bleeding after menopause. Women who have had a positive test result in the past may need screening every six months.

Other women also benefit from the Pap test. Women over age 60 account for 25% of new cases of cervical cancer and 40% of deaths from this disease. Even women who have had a hysterectomy (removal of the uterus) may need to have Pap tests, especially if the surgery was for cancer. (Some women have the cervix left in place after hysterectomy.) Finally, pregnant women should have a Pap test as part of their first prenatal examination.

The Pap test is a screening test. It detects women who are at increased risk of cervical dysplasia (abnormal cells) or cervical cancer. Only an examination of the cervix with a special lighted instrument (colposcopy) and samples of cervical tissue (biopsies) can actually diagnose these problems.

Abnormal results of a pap smear

Abnormal cells found on the Pap test may be described using two different grading systems. Although this can be confusing, the systems are quite similar. The "Bethesda" system is based on the term "squamous intraepithelial lesion" (SIL). Precancerous cells are classified as "atypical squamous cells of undetermined significance," "low-grade" SIL, or "high-grade" SIL. Low-grade SIL includes mild dysplasia (abnormal cell growth) and abnormalities caused by HPV; high-grade SIL includes moderate or severe dysplasia and carcinoma in situ (cancer that has not spread beyond the cervix).

Another term that may be used is "cervical intraepithelial neoplasia" (CIN). In this classification system, mild dysplasia is called CIN I, moderate is CIN II, and severe dysplasia or carcinoma in situ is CIN III.

Regardless of terminology, it is important to remember that an abnormal (positive) result does not necessarily indicate cancer. Results may be falsely abnormal after infection or irritation of the cervix. Fully 60-70% of abnormal results resolve by themselves, and only 1% of mild abnormalities ever develop into cancer.