What Is a Pap Smear?
Cancer of the cervix (cervical cancer) is the fourth most common cause of cancer-related death among women worldwide. The best way to detect cervical cancer is by having regular Papanicolaou tests (Pap smears), or cervical cytology. (Pap is a shortened version of Dr. George Papanicolaou, the doctor who developed the screening test.) A Pap smear is a microscopic examination of cells taken from the uterine cervix.
A Pap test can detect certain viral infections such as human papillomavirus (HPV), which is known to cause cervical cancer. Early treatment of precancerous changes (cervical dysplasia) detected on the Pap smear can stop cervical cancer before it fully develops. A woman may have cervical cancer and not know it because she may not have any symptoms.
The incidence of cancer and deaths from cervical cancer has significantly declined over the years because of prevention, screening, and early detection by the Pap test. Most abnormal Pap smear results indicate the early stages of disease and need reasonable observation by a doctor.
Risk factors for cervical cancer include conditions that increase the likelihood of being infected with a cancer-causing form of human papillomavirus as well as other factors including the following:
- Multiple sexual partners (or sexual partners who have had multiple partners)
- Starting sexual intercourse at an early age
- Weakened immune system
- Previous cancer of the lower genital tract
New recommendations were published in March, 2012 by the U.S. Preventive Service Task Force with agreement by the American Cancer Society (details are described further in this article). Briefly stated, cervical cancer screening is now recommended every 3 years starting at age 21. Cervical cancer screening may be carried out every 5 years for women over age 30 if a Pap test and HPV test are performed.
No upper age limit for cervical cancer screening exists because the incidence of cancer of the cervix increases with age at a time when women may be less likely to get a Pap smear. Diagnosis of most of these cancers is in women older than 50 years. Even after menopause, a woman should continue to have regular Pap testing. Women over age 65 who have had three or more normal Pap tests in a row and no abnormal Pap test results in the last 10 years may choose to stop having Pap tests.
If a woman has had her uterus removed, she should still have yearly screening tests if there is a history of advanced precancerous changes seen on Pap smear or other lower genital tract cancer.
What Are the Risks of a Pap Smear Test?
The Pap smear procedure is not complicated or painful. The only risk is not detecting cervical cancer in time to treat and cure it.
How Do I Prepare for a Pap Smear Test?
The best time to have a Pap smear is when the woman is not menstruating.
For two days before the Pap test, avoid the following because these might interpretation of the test more difficult:
- Vaginal medications (except as directed by your doctor)
- Vaginal contraceptives such as birth control foams, creams, or jellies
What Happens During the Pap Smear Procedure?
A Pap smear is usually part of a pelvic exam and accompanied by a breast exam performed by the health care professional. It should only take about one minute to perform a Pap smear during this overall exam.
- The woman will lie on the examination table (see Multimedia File 1) on her back with her knees up and bent and her feet in stirrups (rests). While she is lying on an examination table, her health care provider will use a small metal or plastic instrument called a speculum to open the vagina so that the walls of the vagina and cervix can be seen clearly.
- A sample of cervical cells and mucus will be obtained from the cervix (see Multimedia File 2) (the part of the uterus that extends into the vagina) and endocervix (the opening of the cervix) using a wooden scraper or a small cervical brush or broom.
- Formerly, a sample of cells was evenly applied to a glass slide and sprayed with a fixative. This sample was sent to the lab for close and careful examination under a microscope. Currently almost all providers are using a new kind of Pap smear called a ThinPrep test, the sample is rinsed into a vial and sent to a lab for slide preparation and examination.
- A cytologist (a specialist trained to look at the cells and interpret a Pap smear) reviews both types of tests.
- Some discomfort during the test may occur. Most women feel nothing at all or feel pressure. Staying relaxed will help stop any discomfort. The woman should breathe slowly and concentrate on relaxing her stomach and legs.
- A Pap smear should not be painful. If a woman has pain during the test, she should tell her doctor.
What Happens After the Pap Smear Procedure? How Do I Interpret My Test Results?
The health care professional will send a letter with test results. If there is a problem, the woman's health care professional may contact her. For peace of mind, she can also call the medical office to get the results. Before leaving after the exam, she can ask how long it takes the office to receive the lab report.
A negative or normal test finding means that the cervix looks healthy. All the cells are of a healthy size and shape.
A positive or abnormal test finding means that something unusual is in the sample. The test found abnormal cells of a different size and shape.
An abnormal Pap smear result does not always indicate cancer. Cells sometimes appear abnormal but are not cancerous. The woman will have to return to the doctor for follow-up care.
- An infection of the cervix may cause an abnormal test result. Yeast, trichomonas, chlamydia, or gonorrhea infection can cause the cervical cells to appear inflamed. After the infection is treated, the Pap smear result usually returns to normal.
- If the Pap smear result is positive because of an infection, the underlying cause should be treated. The test should then be repeated in 2-3 months, because cancer of the cervix can be hidden by an infection. A check-up with a doctor is necessary.
Most laboratories in the United States use a standard set of terms called the Bethesda System to report, or interpret, test results. Under the Bethesda System, Pap smear samples that have no cell abnormalities are reported as "negative for intraepithelial lesion or malignancy" (meaning the woman does not have cancer).
Samples with abnormal cells fall into the following categories (as outlined by the National Cancer Institute):
- ASC (atypical squamous cells): Squamous cells are the thin, flat cells that form the surface of the cervix. The Bethesda System divides this category into the following two groups:
- ASC-US (atypical squamous cells of undetermined significance): The squamous cells do not appear completely normal, but doctors are uncertain what the cell changes mean. Sometimes the changes are related to HPV infection. ACSUS isconsidered a mild abnormality.
- ASC-H (atypical squamous cells cannot exclude a high-grade squamous intraepithelial lesion): The cells do not appear normal, but doctors are uncertain what the cell changes mean. ASC-H may be at higher risk of being pre-cancerous.
- AGC (atypical glandular cells): Glandular cells are mucus-producing cells found in the endocervical canal (opening in the center of the cervix) or in the lining of the uterus. The glandular cells do not appear normal, but doctors are uncertain what the cell changes mean.
- AIS (endocervical adenocarcinoma in situ): Precancerous cells found in the glandular tissue.
- LSIL (low-grade squamous intraepithelial lesion): Low-grade means there are early changes in the size and shape of cells. The word lesion refers to an area of abnormal tissue. Intraepithelial refers to the layer of cells that forms the surface of the cervix. LSILs are considered mild abnormalities caused by HPV infection.
- HSIL (high-grade squamous intraepithelial lesion): High-grade means that there are more marked changes in the size and shape of the abnormal (precancerous) cells, meaning the cells look very different from normal cells. HSILs are more severe abnormalities and have a higher likelihood of progressing to invasive cancer.
When Should I Call the Doctor for Pap Smear Complications?
Early cervical pre-cancers and cancer often have no signs or symptoms. Therefore, it is important to have regular Pap smears. Symptoms usually appear when the cancer has progressed.
The following symptoms must be reported to a health care professional right away:
These symptoms do not always indicate that someone has cancer. Other conditions may cause these symptoms, but a check-up is necessary to determine the cause.
What Is the Pap Smear Follow-up?
If a woman's Pap smear result is normal, she will continue routine screening.
If the Pap smear result is abnormal, the doctor will recommend repeat testing or more frequent follow-up, depending upon the exact type of abnormality and whether any infection is present. The doctor may choose to do a procedure known as a colposcopy.
- In this test, the doctor looks at the cervix through an instrument called a colposcope (a lighted microscope) to look for an explanation for the abnormality in the Pap smear finding. It is performed in the office in a manner similar to the Pap smear, but the doctor uses a special viewing instrument that magnifies the appearance of the surface of the cervix to examine the area for abnormalities.
- The exam is not painful and has no adverse effects. It is possible to perform this exam during pregnancy.
- If there are abnormal findings on the cervix, the doctor will perform a biopsy (take a sample of the tissue to view under a microscope).
- In a biopsy, the doctor will take a small sample of the tissue of the woman's cervix to see if cancer cells are present. A biopsy is the only way to determine if she has precancer, true cancer, or neither.
- Several types of biopsies can be performed under different types of anesthesia.
- To treat precancerous tissue or a very early cancer, the doctor may remove the abnormal tissue entirely during certain types of biopsy methods.
Pap Smear Pictures
Correct position on an exam table for the Pap test. Click to view larger image. The doctor removes cells from the cervix for testing. Click to view larger image.