Pap smear: Screening test for cervical cancer

Understand the importance of the Pap smear, including how it‘s done, what it means when it‘s abnormal and why it needs to be part of your regular health checkups.

A Pap smear, also called a Pap test, is a simple procedure that collects cells from your cervix — the lower, narrow end of your uterus. Named after its developer, George Papanicolaou, M.D., the test effectively detects not only cervical cancer, but also changes in your cervical cells that suggest cancer may develop in the future. Detecting these cells early is your first step in halting the possible development of cervical cancer.

Since women started having Pap smears more than 50 years ago, the number of deaths from cervical cancer has dropped dramatically. What was once the leading cause of cancer death for women in the United States now ranks as No. 15. According to the American Cancer Society, about 3,700 women die each year of cervical cancer — a figure that could drop even further if more women had the Pap smear on a regular basis.

If you get regular Pap smears, you substantially decrease your chances of getting cervical cancer. But even if you develop cervical cancer, the chances of a cure are as high as 90 percent — if discovered early. The Pap smear is the best tool to detect cervical cancer in its earliest stage.

Who should have a Pap smear?

The American Cancer Society recommends that you have your first Pap smear about three years after first having sexual relations or at age 21. After age 21, the guidelines are as follows:

Regardless of your age, if you have certain risk factors you‘ll need to be screened annually. These risk factors include:

• A history of sexual activity as a teenager, especially if you had more than one sex partner
• Multiple sex partners now
• A partner who began sexual activity at an early age or who had many previous sexual partners
• A history of a sexually transmitted disease
• A family history of cervical cancer
• A diagnosis of cervical cancer or a Pap smear that showed precancerous cells
• Infection with human papillomavirus (HPV)
• Tobacco use
• Exposure to diethylstilbestrol (DES) before birth
• HIV infection
• Weakened immune system due to such factors as an organ transplant, chemotherapy or chronic corticosteroid use

If you‘ve had a total hysterectomy — surgical removal of the uterus including the cervix — ask your doctor if you need to continue having Pap smears. If your hysterectomy was performed for a noncancerous condition, such as fibroids, you may be able to discontinue routine Pap smears. If your hysterectomy was for a precancerous or cancerous condition, your vaginal canal still should be checked for abnormal changes.

Preparing for a Pap smear

To ensure that your Pap smear is most effective, follow these tips prior to your test:

• Avoid intercourse, douching or using any vaginal medicines or spermicidal foams, creams or jellies for two days before having a Pap smear, as these may wash away or obscure abnormal cells.
• Try not to schedule a Pap smear during your menstrual period. Although the test can be done, it‘s best to avoid this particular time of your cycle.

How is a Pap smear done?

A Pap smear is performed in your doctor‘s office and takes only a few minutes. First you lie down on an exam table with your knees bent. Your heels rest in supports called stirrups. Your doctor will gently insert an instrument called a speculum into your vagina. Then he or she will take a sample of your cervical cells and smear them onto a glass slide for microscopic examination.

Your doctor will send the slide to a laboratory, where a cytotechnologist — a person trained to detect abnormal cells — will examine the sample. These technicians work in cooperation with a pathologist — a doctor who specializes in cellular abnormalities. The pathologist is responsible for the final diagnosis.

A newer approach uses a liquid to transfer the sample of cells to the laboratory. Your doctor collects the cells in exactly the same way, but then he or she rinses the instruments in a special liquid, which preserves the cells for examination later. When this sample reaches the laboratory, a technician prepares a microscopic slide that‘s cleaner and more easily interpreted than slides prepared in the traditional method.

Usually your doctor performs a Pap smear during a pelvic examination — a simple procedure that allows your doctor to examine your external genitals, uterus, ovaries, other reproductive organs and rectum. Although pelvic examinations can screen for reproductive problems or abnormalities, only a Pap smear will detect early cervical cancer or precancers.

Your test results

The Pap smear doesn‘t diagnose a disease but instead acts as a screening test to alert your doctor to check further. The words used to describe abnormal cells are carefully chosen to send specific messages to your doctor about risk.

Here are some terms your doctor might use and what your next course of action might be:

• Normal. Your test is negative — no abnormal cells are detected. You won‘t need any further treatment or testing until you‘re due for your next Pap smear and pelvic exam.
• Atypical squamous cells of undetermined significance. Squamous cells are thin and flat and grow on the surface of a healthy cervix. In this case, the Pap smear reveals slightly abnormal squamous cells, but the changes don‘t clearly suggest that precancerous cells are present. With the liquid-based test, your doctor can reanalyze the sample to check for the presence of viruses known to promote the development of cancer, such as HPV. If no viruses are present, the abnormal cells found as a result of the test aren‘t of great concern. If worrisome viruses are present, you‘ll need further testing.
• Squamous intraepithelial lesion. This term is used to indicate that the cells collected from the Pap smear may be precancerous. If the changes are low-grade, the size, shape and other characteristics of the cells suggest that if a precancerous lesion is present, it‘s likely to be years away from becoming a cancer. If the changes are high-grade, there‘s a greater chance that the lesion may develop into cancer much sooner. Diagnostic testing is necessary.
• Atypical glandular cells. Glandular cells produce mucus and grow in the opening of your cervix and within your uterus. Atypical glandular cells may appear to be slightly abnormal, but it‘s unclear whether they‘re cancerous. Further testing is needed to determine the source of the abnormal cells.
• Squamous cancer or adenocarcinoma cells. The cells collected for the Pap smear appear so abnormal that the pathologist is almost certain a cancer is present in the vagina, cervix or, occasionally, the uterus. Squamous refers to cancers arising in the flat surface cells of the cervix. Adenocarcinoma refers to cancers arising in glandular cells. If such cells are found, your doctor immediately investigates further.

Upon finding an abnormality, your doctor may decide to examine the tissues through a special microscope in a procedure called colposcopy and take a tissue sample (biopsy). Colposcopy often provides a definitive diagnosis.

Trusting the test results

A Pap smear isn‘t foolproof. You could receive false-negative results. This means that the test indicates that no abnormal cells are present, even though you do have atypical cells. Estimates for the occurrence of false-negative results with a conventional Pap smear vary widely but are at least 5 percent — or one in every 20 women. The liquid-based Pap test provides fewer false-negative results. With either test, false-positive results are extremely rare.

A false-negative result doesn‘t mean that a mistake was made. Many factors can cause a false-negative result, including:

• An inadequate collection of cells
• A small number of abnormal cells
• An inaccessible location of the lesion
• A small lesion
• Abnormal cells mimicking benign cells
• Blood or inflammatory cells obscuring the abnormal cells

Although abnormal cells may go undetected, time is on your side. Cervical cancer takes several years to develop. And if one test doesn‘t detect the abnormal cells, the next test most likely will.