The Pap Test: Questions and Answers
- What is a Pap test?
The Pap test (sometimes called a Pap
smear) is a way to examine cells
collected from the cervix (the lower, narrow end of the uterus).
The main purpose of the Pap test is to detect cancer or abnormal cells that
may lead to cancer. It can also find noncancerous conditions, such as infection
- What is a pelvic exam?
In a pelvic exam, the uterus, vagina,
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
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 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 (or smear) 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.
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
to remove the uterus and cervix) do not need to have a Pap test, unless the
surgery was done as a treatment for precancer or cancer.
- 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.
If her period starts on the day of the test, she should call the doctor right
away and reschedule the appointment. For about 2 days before a Pap test, she
should avoid douching or using vaginal medicines or spermicidal foams, creams,
or jellies (except as directed by a physician). These may wash away or hide
abnormal cells. Also, a woman should not have sexual intercourse for 1 to
2 days before a Pap test, because this may cause unclear results. After the
test, she can go back to her normal activities and return to work right away.
- 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
Samples with cell abnormalities are divided into the following categories:
- 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 groups:
- 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 human
papillomavirus (HPV) infection (see Question 13). ACS–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.
How common are Pap test abnormalities?
- 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 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
means that there are more marked changes in the size and shape of the abnormal
(precancerous) 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 (6 percent) are abnormal and require medical
What do abnormal results mean?
A physician may simply describe Pap test results to a patient as "abnormal."
Cells on the surface of the cervix sometimes appear abnormal but are very
rarely cancerous. It is important to remember that abnormal conditions do
not always become cancerous, and some conditions are more likely to lead to
cancer than others. A woman may want to ask her doctor for specific information
about her Pap test result and what the result means.
There are several terms that may be used to describe abnormal results.
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
intraepithelial lesion (SIL) 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 (early changes in the size, shape, and number of cells) or high-grade
(precancerous cells that look very different from normal cells).
intraepithelial neoplasia (CIN) 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
(1 to 3), 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.
What if Pap test results are abnormal?
If the Pap test shows an ambiguous or minor abnormality, the physician may
repeat the test to determine whether further follow-up is needed. Many times,
cell changes in the cervix go away without treatment. In some cases, doctors
may prescribe estrogen
cream for women who have ASC–US and are near or past menopause.
Because these cell changes are often caused by low hormone
levels, applying an estrogen cream to the cervix for a few weeks can usually
help to clarify the cause of the cell changes.
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 (called a colposcope)
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. If the colposcopy finds
abnormal tissue, the physician may perform endocervical
curettage or a biopsy.
Biopsy is the removal of cells or tissues from the abnormal area for examination
under a microscope. Endocervical curettage is a type of biopsy that involves
scraping cells from inside the endocervical canal with a small spoon-shaped
tool called a curette.
If the testing shows 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:
How do terms for Pap test abnormalities compare, and which tests and treatment
options may be appropriate?
- LEEP (loop
electrosurgical excision procedure) is surgery that uses an electrical
current which is passed through a thin wire loop to act as a knife.
destroys abnormal tissue by freezing it.
therapy is the use of a narrow beam of intense light to destroy
or remove abnormal cells.
removes a cone-shaped piece of tissue using a knife, a laser,
or the LEEP technique.
How are human papillomaviruses associated with
the development of cervical cancer?
|Pap Test Result
|Also Known As
||Tests and Treatments May Include
| Atypical squamous cells–undetermined significance
- HPV testing
- Repeat Pap test
- Colposcopy and biopsy
- Estrogen cream
| Atypical squamous cells–cannot exclude HSIL
| Atypical glandular cells
- Colposcopy and biopsy and/or endocervical curettage
| Endocervical adenocarcinoma in situ
- Colposcopy and biopsy and/or endocervical curettage
| Low-grade squamous intraepithelial lesion
- Mild dysplasia
- Cervical intraepithelial neoplasia–1 (CIN–1)
| High-grade squamous intraepithelial lesion
- Moderate dysplasia
- Severe dysplasia
- Carcinoma in situ (CIS)
- Colposcopy and biopsy and/or endocervical curettage
- Further treatment with LEEP, cryotherapy, laser therapy, conization,
Human papillomaviruses (HPVs) are a group of more than 100 viruses.
Some types of HPV cause the common warts
that grow on hands and feet. Over 30 types of HPV can be passed from one person
to another through sexual contact. Some of these sexually transmitted HPVs
cause wart-like growths on the genitals but do not lead to cancer. About 15
sexually transmitted HPVs are referred to as "high-risk" because they are
more likely to lead to the development of cancer.
HPV infection is the primary risk factor for cervical cancer. About 6 million
new genital HPV infections occur each year in the United States. However,
although HPV infection is very common, only a very small percentage of women
with untreated HPV infections develop cervical cancer.
Who is at risk for HPV infection?
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 (HIV) 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.
Does infection with a cancer-associated type of HPV always lead to a precancerous
condition or cancer?
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 follow-up care by trained
clinicians, women with precancerous cervical abnormalities can be treated
before cancer develops.
Do women who have been vaccinated against HPVs still need
to have Pap tests?
Yes. Pap tests continue to be essential to detect cervical cancers and precancerous
changes, even in women who have been vaccinated against HPVs.
Food and Drug Administration (FDA) recently approved Gardasil®, a
that is highly effective in preventing infection with four types of HPV. Two
of these four HPVs cause about 70 percent of cervical cancers, and the other
two HPVs cause about 90 percent of genital warts (1). Another
promising vaccine, Cervarix™, is being tested but is not yet approved by
the FDA. These vaccines do not protect against all HPV types that cause cervical
cancer. In addition, they do not protect or treat women who are already infected
with HPV. Therefore, it is important for vaccinated women to continue to undergo
cervical cancer screening
as is recommended for women who have not been vaccinated.
Have any studies been done to examine HPV testing and treatment options
for mild Pap test abnormalities?
Cancer Institute (NCI), a component of the National
Institutes of Health (NIH), funded and organized the ASCUS/ LSIL
Triage Study (ALTS), a major clinical
trial (research study with people). Findings of the trial indicate that
performing an HPV test on cervical samples from women with ASC–US is
more efficient than performing an immediate colposcopy or a repeat Pap test
for identifying which ASC-US abnormalities need treatment. In women with ASC-US,
a negative HPV test can provide reassurance that cancer or a precancerous
condition is not present.
What are false positive and false negative results?
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.
What methods are being developed to improve the accuracy of Pap tests?
In April 1996, the Consensus Development Conference on Cervical Cancer, which
was convened by the NIH, 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
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
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.
- Koutsky LA, Ault KA, Wheeler CM, et al. A controlled trial
of a human papillomavirus type 16 vaccine. New England Journal of Medicine
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