The Pap Test

Since it first came into use 50 years ago, the Pap test has lowered the number of deaths from cancer of the cervix by 70 percent in the U.S. The Pap test detects changes in the cells of the cervix (the opening of a woman's uterus). These changes could lead to cancer. The Pap test helps find these changes early so they can be treated before they become serious. By having a Pap test, a woman can help prevent cancer of the cervix.

This page tells you:

  • Who should have a Pap test
  • How often the test should be done
  • What the results mean

The Pap test is the best way to find changes that may lead to cervical cancer.

The Cervix

The cervix is the lower, narrow end of the uterus. It opens into the vagina. The cervix is covered by a thin layer of tissue (like the skin inside your mouth). As with all cells, the cells that make up this tissue grow all the time. During this growth, the cells at the bottom layer slowly move to the surface of the cervix. When these cells reach the surface, they are shed. During this process, some cells can become abnormal.

For the Pap test, a sample of cells is taken from the surface of the cervix. The test can find abnormal cells that could lead to cancer of the cervix and the vagina. It is not used to detect cancer in other parts of the body.

A Regular Part of Your Health Care

Having a regular Pap test is an important part of your overall health care. When you start having the test and how often you have it depends on your history. You should have your first Pap test by age 18 or when you start having sex with men - whichever comes first.
Pap tests should continue past menopause. If your tests show abnormal results or if you have had cancer, your doctor may advise you to have a Pap test more often. If you have had a hysterectomy for benign (not cancer) disease, you should still have the Pap test if you have any of the risk factors listed.

Some women have a higher risk of developing cervical changes. Your risk may be higher if you:

  • Have had more than one sexual partner or a male sexual partner who has had more than one partner;
  • Had intercourse for the first time at an early age;
  • Have had certain sexually transmitted diseases (STDs), such as genital warts (human papillomavirus) or herpes;
  • Are infected with human immunodeficiency virus (HIV) or have a weakened immune system (such as a transplant patient);
  • Smoke cigarettes.

If you have any of these risk factors, it is important for you to have a Pap test each year. If you have no risk factors and have had three normal tests in a row, your doctor may suggest you have the test done less often. You should still see your doctor each year for a pelvic exam. Abnormal cells may go through several stages of change before cervical cancer appears. This usually happens over a number of years. If cancer does occur, symptoms may include bleeding, pelvic pain or discharge. In most cases there are no symptoms, though.

The Test

For the Pap test, a speculum is inserted into the vagina. A small sample of cells is collected with a small brush or swab and scraper. The brush or swab is inserted into the cervical canal to reach the higher cells. The Pap test can be done during a pelvic exam. Do not douche or use vaginal medication, spermicides or lubrication for 2 to 3 days before the test. These products may wash away or hide any changed cells. It is best to schedule the Pap test for a time when you're not having your menstrual period.

A speculum will be inserted into your vagina. This device gently opens the vagina so the cervix can be seen. A small brush and scraper are used to remove cells from the inside and outside of the cervix. You will not feel any pain.

The cell sample is then placed on a glass slide to be sent to the lab for testing. A technician or doctor uses a microscope to look for cells that do not appear normal. The results are classified based on how the cells look. Your health insurance often will pay for this Pap test.

There are several new methods designed to improve the accuracy of test results. Your doctor may suggest you use one of them. One method sends the cells to the lab in a bottle of liquid. The cells then are transferred to a slide and read in the standard way. Other methods use the help of a computer to find abnormal cells. It is not clear that these methods detect cervical cancer better than the standard Pap test. Your insurance company may not pay for these newer types of tests.

The Results

A false-positive result shows a problem when there isn't one. A false-negative result shows there isn't a problem when there really is one.

The results of your Pap test are most often classified by a system developed by the National Cancer Institute. The classification of the cells helps doctors plan treatment:

  • Normal: Only normal cells were seen on your Pap test.
  • ASCUS (Atypical squamous cells of undetermined significance): Changes were seen in cells lining the outer cervix.
  • AGUS (Atypical glandular cells of undetermined significance): Changes were seen in the cells lining the inner cervix.
  • Squamous intraepithelial lesion (SIL): The cells that were tested show certain levels and changes. SIL can be low grade or high grade.
    • Low-grade SIL includes mild changes and changes linked to human papillomavirus. Some types of these viruses have been linked to cancer of the cervix.
    • High-grade SIL includes moderate and severe changes and very early "precancer".
  • Cancer: The cells have spread into other tissues.

This enlarged view of cervical cells shows abnormal cells (middle) growing toward the surface of the cervix.

Is the Pap Test Always Accurate?

Like any test, the Pap test is not always accurate. It may report abnormal cells are present when they aren't. This is known as a false-positive result. A Pap test may also miss abnormal cells - known as a false-negative.
False-negative results can occur for a number of reasons:

  • The sample contains too few or too many cells
  • An infection or blood covered up abnormal cells
  • Douching or vaginal medicines have washed away abnormal cells

Because Pap test results are based on how cells on a slide look, even experts may not agree. Sometimes the reason for false-negative results is not known. Your doctor may suggest a test be repeated.


If the lab reports any abnormal finding, the doctor may arrange for further tests. This may be as simple as a repeat Pap test in a few weeks or a few months. In the lab, a technician or doctor uses a microscope to study the cell sample. Sometimes your doctor will do an exam called a colposcopy to decide if you need treatment. A magnifying device called a colposcope is used to look at the cervix. With this device, your doctor may be able to see changes that suggest abnormal cells.

Colposcopy may help the doctor decide whether a cervical biopsy needs to be done. For a biopsy, the doctor removes some of the cells to be studied under a microscope. You may feel a little pain during the biopsy. Treatment depends on the findings. In many cases, all that is required is to remove a thin layer of cells from the surface of the cervix. New cells often are normal and no further treatment is needed.


The Pap test is the best way to find changes that may lead to cervical cancer. Finding abnormal cells can help prevent cancer of the cervix. Only a very small number of women with abnormal Pap test results have cancer. By understanding the Pap test and how results are reported, you can take an active part in your health care.


Biopsy: A minor surgical procedure to remove a small piece of tissue that is then examined under a microscope.

Colposcopy: Viewing of the cervix, vulva, or vagina using magnification with a special instrument.

Human Immunodeficiency Virus (HIV): A virus that attacks certain cells of the body's immune system and causes acquired immunodeficiency syndrome (AIDS).

Human Papillomavirus (HPV): The common name for a group of related viruses. Some of these viruses cause genital warts and are linked to cervical changes and cancer.

Squamous Intraepithelial Lesion (SIL): A condition that occurs when normal cells on the surface of the cervix are replaced by a layer of abnormal cells. SIL is classified as high grade or low grade. It is not cancer.

This excerpt from ACOG's Patient Education Pamphlet is provided for your information. It is not medical advice and should not be relied upon as a substitute for visiting your doctor. If you need medical care, or have any questions, please contact your obstetrician-gynecologist. Copyright (c) 2000 The American College of Obstetricians and Gynecologists.

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