The Pap Test: Questions and Answers
- What is a Pap test? The Pap test is a way to examine cells collected from the cervix. The main purpose of the Pap test is to find abnormal cell changes that may arise from cervical cancer or before cancer develops.
- What is a pelvic exam? In a pelvic exam, the uterus, vagina, ovaries, fallopian tubes, bladder, and rectum are felt to find any abnormality in their shape or size. During a pelvic exam, an instrument called a speculum is used to widen the vagina so that the upper portion of the vagina and the cervix can be seen.
- Why are a Pap test and pelvic exam important? A Pap test and pelvic exam are important parts of a woman’s routine health care because they can detect abnormalities that may lead to invasive cancer of the cervix. These abnormalities can be treated before cancer develops. Most invasive cancers of the cervix can be prevented if women have Pap tests regularly. Also, as with many types of cancer, cancer of the cervix is more likely to be treated successfully if it is detected early.
- Who performs a Pap test? Doctors and other specially trained health care professionals, such as physician assistants, nurse midwives, and nurse practitioners, may perform Pap tests and pelvic exams. These individuals are often called clinicians.
- How is a Pap test done? A Pap test is simple, quick, and painless; it can be done in a doctor’s office, a clinic, or a hospital. While a woman lies on an exam table, the clinician inserts a speculum into her vagina to widen it. A sample of cells is taken from the cervix with a wooden scraper and/or a small cervical brush. The specimen is placed on a glass slide and preserved with a fixative, or is rinsed in a vial of fixative, and is sent to a laboratory for examination.
- How often should a woman have a Pap test? Women should talk with their clinician about when and how often they should have a Pap test. Current general guidelines recommend that women have a Pap test at least once every 3 years, beginning about 3 years after they begin to have sexual intercourse, but no later than age 21. Experts recommend waiting about 3 years after the start of sexual activity to avoid overtreatment for common, temporary abnormal changes. It is safe to wait 3 years, because cervical cancer usually develops slowly. Cervical cancer is extremely rare in women under age 25.
- When should the Pap test be done? A woman should have this test when she is not menstruating; the best time is between 10 and 20 days after the first day of the last menstrual period. For about 2 days before a Pap test, she should avoid douching or using vaginal medicines or spermicidal foams, creams, or jellies. These may wash away or hide abnormal cells.
- How are the results of a Pap test reported? Most laboratories in the United States use a standard set of terms called the Bethesda System to report test results. Under the Bethesda System, Pap test samples that have no cell abnormalities are reported as “negative for intraepithelial lesion or malignancy.” Samples with cell abnormalities are divided into the following categories:
Women ages 65 to 70 who have had at least three normal Pap tests and no abnormal Pap tests in the last 10 years may decide, after talking with their clinician, to stop having Pap tests. Women who have had a hysterectomy do not need to have a Pap test, unless the surgery was done as a treatment for precancer or cancer.
- 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 two
- ASC–US—atypical squamous cells of undetermined significance. The squamous cells do not appear completely normal, but doctors are uncertain about what the cell changes mean. Sometimes the changes are related to HPV infection. ASC–US are considered mild abnormalities.
- ASC–H—atypical squamous cells cannot exclude a high-grade squamous intraepithelial lesion. The cells do not appear normal, but doctors are uncertain about what the cell changes mean. ASC–H may be at higher risk of being precancerous.
- AGC—atypical glandular cells. Glandular cells are mucus-producing cells found in the endocervical canal or in the lining of the uterus. The glandular cells do not appear normal, but doctors are uncertain about what the cell changes mean.
- AIS—endocervical adenocarcinoma in situ. Precancerous cells are 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 cells, meaning that the cells look very different from normal cells. HSILs are more severe abnormalities and have a higher likelihood of progressing to invasive cancer.
About 55 million Pap tests are performed each year in the United States. Of these, approximately 3.5 million are abnormal and require medical followup.
There are several terms that may be used to describe abnormal results.
- Dysplasia is a term used to describe abnormal cells. Dysplasia is not cancer, although it may develop into very early cancer of the cervix. The cells look abnormal under the microscope, but they do not invade nearby healthy tissue. There are four degrees of dysplasia, classified as mild, moderate, severe, or carcinoma in situ, depending on how abnormal the cells appear under the microscope. Carcinoma in situ means that cancer is present only in the layer of cells on the surface of the cervix, and has not spread to nearby tissues.
- Squamous intraepithelial lesion is another term that is used to describe abnormal changes in the cells on the surface of the cervix. The word squamous describes thin, flat cells that form the outer surface of the cervix. The word lesion refers to abnormal tissue. An intraepithelial lesion means that the abnormal cells are present only in the layer of cells on the surface of the cervix. A doctor may describe SIL as being low-grade or high-grade.
- Cervical intraepithelial neoplasia is another term that is sometimes used to describe abnormal tissue findings. Neoplasia means an abnormal growth of cells. Intraepithelial refers to the layer of cells that form the surface of the cervix. The term CIN, along with a number, describes how much of the thickness of the lining of the cervix contains abnormal cells.
- Atypical squamous cells are findings that are unclear, and not a definite abnormality.
Cervical cancer, or invasive cervical cancer, occurs when abnormal cells spread deeper into the cervix or to other tissues or organs.
If the Pap test shows a finding of ASC–H, LSIL, or HSIL, the physician may perform a colposcopy using an instrument much like a microscope to examine the vagina and the cervix. The colposcope does not enter the body. During a colposcopy, the physician may coat the cervix with a dilute vinegar solution that causes abnormal areas to turn white. The physician may also perform a biopsy.
The physician may also perform endocervical curettage. This test involves scraping cells from inside the endocervical canal with a small spoon-shaped tool called a curette. The doctor may also remove a small piece of cervical tissue for examination. This procedure is called a biopsy. The cells or tissue are sent to a lab for study under a microscope.
If the lab finds abnormal cells that have a high chance of becoming cancer, further treatment is needed. Without treatment, these cells may turn into invasive cancer. Treatment options include the following:
- LEEP is surgery that uses an electrical current which is passed through a thin wire loop to act as a knife.
- Cryotherapy destroys abnormal tissue by freezing it.
- Laser therapy is the use of a narrow beam of intense light to destroy or remove abnormal cells.
- Conization removes a cone-shaped piece of tissue using a knife, a laser, or the LEEP technique.
|Pap Test Result||Abbreviation||Also Known As||Tests and Treatments May Include|
|Atypical squamous cells–undetermined signficance||ASC–US||HPV testing Repeat Pap test Colposcopy and biopsy Estrogen cream|
|Atypical squamous cells–cannot exclude HSIL||ASC–H||Colposcopy and biopsy|
|Atypical glandular cells||AGC||Colposcopy and biopsy and/or endocervical curettage|
|Endocervical adenocarcinoma in situ||AIS||Colposcopy and biopsy and/or endocervical curettage|
|Low-grade squamous intraepithelial lesion||LSIL||Mild dysplasia or Cervical intraepithelial neoplasia–1||Colposcopy and biopsy|
|High-grade squamous intraepithelial lesion||HSIL||Moderate dysplasia, Severe dysplasia, CIN–2, CIN–3, or Carcinoma in situ||Colposcopy and biopsy and/or endocervical curettage Further treatment with LEEP, cryotherapy, laser therapy, conization, or hysterectomy|
HPV infection is the primary risk factor for cervical cancer. However, although HPV infection is very common, only a very small percentage of women with untreated HPV infections develop cervical cancer.
HPV infection is more common in younger age groups, particularly among women in their late teens and twenties. Because HPVs are spread mainly through sexual contact, risk increases with number of sexual partners. Women who become sexually active at a young age, who have multiple sexual partners, and whose sexual partners have other partners are at increased risk. Women who are infected with the human immunodeficiency virus are also at higher risk for being infected with HPVs and for developing cervical abnormalities. Nonsexual transmission of HPVs is rare. The virus often disappears but sometimes remains detectable for years after infection.
No. Most HPV infections appear to go away on their own without causing any kind of abnormality. However, persistent infection with cancer-associated HPV types increases the risk that mild abnormalities will progress to more severe abnormalities or cervical cancer. With regular followup care by trained clinicians, women with precancerous cervical abnormalities can be treated before cancer develops.
Findings of the ASCUS/LSIL Triage Study, a major clinical trial funded and organized by the National Cancer Institute, suggest that HPV testing in women with ASC–US may help identify underlying abnormalities that need a doctor’s attention. The study results suggest that testing cervical samples for HPVs can identify which ASC–US abnormalities need treatment. A negative HPV test can provide reassurance that cancer or a precancerous condition is not present.
The Pap test is a screening test and, like any such test, it is not 100-percent accurate. Although false positive and false negative results do not occur very often, they can cause anxiety and can affect a woman’s health.
A false positive Pap test means that a patient is told she has abnormal cells, but the cells are actually normal. A false negative Pap test occurs when a specimen is called normal, but the woman has a significant abnormality that was missed. A false negative Pap test may delay the diagnosis and treatment of a precancerous condition. However, regular screening helps to compensate for the false negative result. If abnormal cells are missed at one time, chances are good that the cells will be detected the next time.
In April 1996, the Consensus Development Conference on Cervical Cancer, which was convened by the National Institutes of Health, concluded that about half of false negative Pap tests are due to inadequate specimen collection. The other half are due to a failure to identify or interpret the specimens correctly. Although the conventional Pap test is effective in the majority of cases, the conference made it clear that new methods of collecting and reading specimens are needed to reduce the number of false negatives.
The Bethesda System requires laboratories to determine whether there are enough cervical cells in the specimen to make a proper evaluation. This requirement helps improve the quality of samples and sample collection. The Bethesda System requires a sample to be categorized as “satisfactory for evaluation” or “unsatisfactory for evaluation.”
One new method of collecting and analyzing samples is called liquid-based thin-layer slide preparation. This method may make it easier to screen for abnormal cells. Cervical cells are collected with a brush or other collection instrument. The instrument is rinsed in a vial of liquid preservative. The vial is sent to a laboratory, where an automated thin-layer slide device prepares the slide for viewing. Results of this method suggest that it is comparable to, or more sensitive than, standard Pap tests for the detection of significant abnormalities.
Computer automated readers are also being used to improve the reading of Pap tests. This technology uses a microscope that conveys a cellular image to a computer, which analyzes the image for the presence of abnormal cells