Most women should have Pap tests on a regular basis. Regular Pap tests can help find problems early when they can be treated before they become serious. This pamphlet explains:

Why a Pap test is done Who should have a Pap test What the results mean

The Pap test is the best way to find cell changes that may lead to cancer of the cervix.

The Cervix

The cervix is the lower, narrow end of a woman's uterus. It opens into the vagina (the birth canal). The cervix is covered by a thin layer of tissue. This tissue is like the skin inside your mouth.

Like all skin cells, those that cover the cervix grow and are replaced all the time. During this growth, the cells at the bottom layer slowly move to the surface. These cells are shed when they reach the surface.

For the Pap test, a speculum is placed into the vagina. A small sample of cells is removed with a small brush or swab and a scraper. The sample is sent to a lab for testing.

What Is a Pap Test?

The Pap test, sometimes called a Pap smear or cervical cytology screening, is a simple test to look at cells taken from the cervix. It tells your doctor if there are any abnormal cells on the cervix that may lead to cancer. The Pap test does not detect cancer in other parts of the body.

A Pap test is simple and fast. It is most often done in a doctor's office or a clinic during a pelvic exam. With the woman lying on an exam table, a speculum is used to gently open the vagina. This device lets the doctor see the cervix and upper vagina.

A small number of cells are removed from the cervix by gently scraping the surface with a brush or spatula. The cell sample is then sent to a lab for testing.

The cell sample is placed on a glass slide before it is sent to the lab. The cells also may be put in a liquid and sent to a lab, where they are then placed on a slide.

At the lab, the sample is carefully examined using a microscope to see if abnormal cells are present. A few labs use a computer to do the initial exam.

The Pap test only finds abnormal cells that are present in the cervix. It cannot detect cancer or other problems in other parts of the body.

Who Should Have a Pap Test?

Pap tests are an important part of all women's health care. When and how often you have the test depends on your age and health history. You should have routine Pap tests if:

• You are 21 years of age or older or
• You became sexually active at least 3 years ago, even if you are younger than 21 years of age or are not having sex now

How Often Do You Need a Pap Test?

All women should have a pelvic exam yearly. When a woman has a pelvic exam with a speculum, a Pap test may or may not be done. Be sure you know if a Pap test has been included in your exam.

Talk with your doctor about whether and how often you should have a Pap test. Women younger than 30 years should have a Pap test every year. If you are older than 30 years and have had three normal Pap tests in a row, you may not need a Pap test every year. You may only need one every 2 or 3 years. If the results of your Pap test are abnormal, or if you have had abnormal results in the past, your doctor may suggest having a Pap test more often. Certain risk factors might mean that you should be tested every year, even if you have had several normal results (see box). If you have had a hysterectomy, talk to your doctor about whether you still need a routine Pap test.

The Test Results

Most labs in the United States use the "Bethesda System" to describe Pap test results. This standard system helps doctors plan treatment if needed. Under this system, your results will be placed in one of several groups:

• Normal (negative): Only normal cells are seen. There are no signs of cancer or precancer. Cells are called precancerous when there are changes in them that may, but do not always, become cancer.
• Atypical squamous cells (ASC): Some cells were seen that cannot be called normal, but do not meet the requirements to call them precancer. The abnormal cells may be caused by an infection, irritation, intercourse, or may be precancerous.
• SIL (squamous intraepithelial lesion): Changes were seen in the cells that may show signs of precancer. SIL can be low grade or high grade.
  • Low-grade SIL (LSIL): Early, mild changes were seen in the size or shape of cells.
  • High-grade SIL (HSIL): Moderate or severe cell changes are seen. HSIL changes on a Pap test suggest an increased risk of "precancer" being present than with LSIL changes.
• Atypical glandular cells: Cell changes were seen that represent an abnormality that needs to be evaluated more closely. The type of evaluation depends on your age and other factors.
• Cancer: Abnormal cells were seen to have spread deeper into the cervix or to other tissues. They have become a true cancer. You will need a thorough evaluation and treatments.

Risk Factors Previously treated for cancer Human immunodeficiency virus (HIV) infection Weakened immune system (for instance, because you have had a kidney transplant) Exposure to the drug diethylstilbestrol (DES) before birth

Follow-Up

Cells taken from the surface of the cervix sometimes look abnormal. Usually abnormal cells are not cancer. Abnormal cells may go through many stages of change before cervical cancer appears. This often happens over a number of years.

If the lab finds abnormal cells, your doctor may suggest more tests. This may be as simple as a repeat Pap test.

Your doctor also may want to test for human papillomavirus (HPV). HPV is a group of related viruses, a few of which are linked to cervical changes. Recent studies have shown some types of HPV to cause cancer of the cervix. Most women with HPV do not develop precancer of the cervix. Genital HPV can be passed from person to person through sexual contact.

In some cases, the HPV test can be done to help clarify the Pap test results. A negative HPV test result often means that the cell changes that were seen are not related to precancer. Sometimes the sample taken for your Pap test also can be used for an HPV test. In this case, you would not need to see the doctor again for your HPV test.

Sometimes an exam called a colposcopy may be advised. This exam uses a device like a microscope to look at the cervix. It helps your doctor see changes that may mean abnormal cells are present. Colposcopy is done in a doctor's office.

If an area of abnormal cells is seen, your doctor may decide that a cervical biopsy is needed. For a biopsy, the doctor removes a small sample of tissue and sends it to a lab to be studied. Colposcopy and biopsy will help your doctor decide if treatment is needed.

Treatment depends on the test results. A woman often can be treated in her doctor's office. Talk with your doctor if you have questions about your Pap test or other test results.

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

Is the Pap Test Always Accurate?

As with any lab test, Pap test results are not always accurate. Sometimes, the results show abnormal cells when the cells are normal. This is called a "false-positive" result. A Pap test also may fail to detect abnormal cells when they are present. This is called a "false-negative" result.

Many factors can cause false results. For instance:

• The sample may contain too few cells
• There may not be enough abnormal cells to study
• An infection or blood may hide abnormal cells
• Douching or vaginal medicines may wash away or dilute abnormal cells
• Problems with the way the slides were prepared for study

Routine Pap tests help lower the chance that abnormal cells are missed. If a Pap test misses abnormal cells this year, they may be found on your next Pap test.

Finally . . .

The Pap test is the best way to find cell changes that may lead to cancer of the cervix. Routine Pap tests can help find problems early. If a Pap test finds abnormal cells, your doctor will suggest further tests or treatment.

Glossary

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

Colposcopy: Viewing of the cervix, vulva, or vagina under magnification with an instrument called a colposcope.

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