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.

Definition

A Pap smear, also called a Pap test, is a procedure to test for cervical cancer in women. A Pap smear involves collecting cells from your cervix — the lower, narrow end of your uterus.

Detecting cervical cancer early with a Pap smear gives you a greater chance at a cure, should cervical cancer be detected. A Pap smear can also detect changes in your cervical cells that suggest cancer may develop in the future. Detecting these cells early with a Pap smear is your first step in halting the possible development of cervical cancer.

Why it's done

A Pap smear is typically done in conjunction with a pelvic examination — a procedure that allows your doctor to examine your external genitals, vagina, uterus, ovaries and rectum. Although pelvic examinations can screen for reproductive problems or abnormalities, only a Pap smear will detect early cervical cancer or precancers.

Who should have a Pap smear?
A number of organizations have recommendations regarding when a woman should have a Pap smear. Groups generally agree that you should have your first Pap smear about three years after first having sexual relations or at age 21, whichever comes first.

After age 21, the groups' guidelines differ slightly because each takes different factors into consideration. Here's a look at Pap smear guidelines from the American Cancer Society (ACS), the American College of Obstetricians and Gynecologists (ACOG) and the U.S. Preventive Services Task Force (USPSTF):

Age	ACS	ACOG	USPSTF
21 to 29	Every two years with a liquid-based test or annually with a conventional test	Annual Pap tests	Pap tests at least every three years
Over 30	Every two or three years if you've had three negative tests in a row	Every two or three years if you've had three negative tests in a row	Pap tests at least every three years

If you have certain risk factors you should undergo a Pap smear annually, regardless of your age. These risk factors include:

A diagnosis of cervical cancer or a Pap smear that showed precancerous cells
Exposure to diethylstilbestrol (DES) before birth
HIV infection
Weakened immune system due to organ transplant, chemotherapy or chronic corticosteroid use

Who can consider stopping Pap smears?
Discuss your screening options with your doctor. In certain situations a woman and her doctor may decide to end Pap testing, such as:

After total hysterectomy. After 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, you should have an annual vaginal Pap smear.
Older age. Groups don't agree whether there's an upper age limit for routine Pap tests. ACS guidelines suggest a woman can stop having tests at 70 if she's had three negative tests in the last 10 years. USPSTF guidelines suggest stopping Pap testing at 65. ACOG guidelines say there isn't enough evidence to determine an age at which it's safe to stop testing. Discuss your options with your doctor and together you can decide what's best for you based on your risk factors.

Risks

A Pap smear is a safe way to screen for cervical cancer. However, a Pap smear isn't foolproof. It's possible to receive false-negative results — meaning that the test indicates no abnormality, even though you do have abnormal 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, in which the sample of cells is preserved in liquid rather than smeared on a microscope slide, provides fewer false-negative results. With either test, false-positive results — when the test indicates an abnormality when there really isn't one — 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 it's possible for abnormal cells to 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.

How you prepare

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 time of your cycle, if possible.

What you can expect

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	Female reproductive system
	Pap smear
	Cervical cells

During the Pap smear
A Pap smear is performed in your doctor's office and takes only a few minutes. You may be asked to undress completely or only from the waist down.

You'll lie down on your back 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. The speculum holds the walls of the vagina apart so that your doctor can easily see your cervix. Inserting the speculum may cause sensation of pressure in your pelvic area. Sometimes the speculum feels cold when it's first inserted.

Then your doctor will take samples of your cervical cells using a soft brush and a flat scraping device called a spatula. This doesn't hurt and you may not even feel the sample being taken.

After the Pap smear
After your Pap smear, you can go about your day without any restrictions.

Depending on the type of Pap test you're undergoing, your doctor transfers the cell sample collected from your cervix onto a glass slide or into a container holding a special liquid to preserve the sample (liquid-based Pap test).

The samples are transferred 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.

Ask your doctor about when you can expect the results of your Pap smear. In some cases, your doctor will only contact you if something of concern is found or if it's determined that you need further testing.

Results

The Pap smear can alert your doctor of suspicious cells that need further testing.

Normal results
If only normal cervical cells were discovered during your Pap smear, you're said to have a negative result. You won't need any further treatment or testing until you're due for your next Pap smear and pelvic exam.

Abnormal results
If abnormal or unusual cells were discovered during your Pap smear, you're said to have a positive result. A positive result doesn't mean you have cervical cancer. What a positive result means depends on the type of cells discovered in your Pap smear.

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

Atypical squamous cells of undetermined significance (ASCUS). Squamous cells are thin and flat and grow on the surface of a healthy cervix. In the case of ASCUS, 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 some types of human papillomavirus (HPV). If no high-risk 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 and their significance.
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 vagina or cervix. Adenocarcinoma refers to cancers arising in glandular cells. If such cells are found, your doctor will recommend prompt evaluation.

If your Pap smear is abnormal, your doctor may perform a procedure called colposcopy using a special magnifying instrument (colposcope) to examine the tissues of the cervix, vagina and vulva. He or she may take a tissue sample (biopsy) from any areas that appear abnormal. The tissue sample is then sent to a laboratory for analysis and a definitive diagnosis.