Pap Test

here it is: the little postcard reminding you that it's time to schedule a physical exam...and your Pap test. It's an easy reminder to cast aside. After all, didn't you have a Pap test just a little while ago? Why have one so often? What exactly does it mean, anyway?

Actually, this little test is one of the most important developments in women's health in decades. It's a screening test for cancer of the cervix; and since its introduction there has been a dramatic decline in deaths from the disease.

A study in British Columbia showed that, for every 100,000 people, there were 13 to 14 deaths per year from cervical cancer in 1958; in 1966, this number decreased to 11 to 12 and in 1974 it was down to 5 to 6, a 50 percent decrease. The most recent statistics show that the mortality from cervical cancer in the United States in 1988 was only 3 per 100,000.

In addition to detecting cancer and precancer, the Pap test may also show evidence of vaginal infections, such as yeast, Trichomonas, or viral infections. If your Pap test suggests inflammation, your doctor may do further tests to identify infections of the uterus, fallopian tubes, or vagina, which sometimes take hold without any warning symptoms. Rarely, the Pap test detects cells being shed from within the uterus (endometrial cells), which could signify excessive growth of this tissue.

When to Have a Pap Test

How often you need a Pap test has been somewhat controversial: the American Cancer Society and the American College of Obstetrics and Gynecology, along with several other health organizations, currently recommend the following: if you are sexually active, or are 18 years of age or more, you should have a Pap test and pelvic exam every year for 3 consecutive years. After 3 normal reports the test can be repeated less often, every 2 to 3 years, depending on your risk for cervical cancer. If you have had a hysterectomy, and as a result do not have a cervix, you may still be advised to have a Pap test from your vaginal walls to detect cancer there.

Reasons for an Annual Test

You are considered to be at increased risk of cervical cancer, and should therefore have a Pap test every year, if you:

• Have HPV (Human Papilloma Virus, the virus that causes genital warts—often detected only by a Pap test since many who carry the virus actually have no warts)
• Smoke
• Began having sex at an early age
• Have had many sexual partners
• Use birth control pills
• Have an impaired immune system (for example, have HIV or AIDS)
• Are being treated with drugs that suppress your immune system
• Have had radiation therapy
• Were born after your mother took DES while carrying you (DES, given years ago to prevent miscarriage, was subsequently discovered to increase the child's risk of cervical or vaginal cancer in later life.)
• Have a sexual partner who is “high­risk” (has genital warts, for instance)

You may be surprised to learn that you are at increased risk. In fact, some of these factors have only recently been discovered, and are still unfamiliar to most women. Doctors are also aware that a few of these factors offer benefits that far outweigh their role in cervical cancer. For example, it would be unwise to discontinue birth control pills given the protection they afford not only against pregnancy, but also against endometrial and ovarian cancer.

How the Test is Done

The Pap test relies on minute samples of tissue from the lining of the cervix; and these samples must be taken from very specific points.

The cervix is actually the lowermost part of the uterus. A cylinder projecting into the vagina, it surrounds a tiny canal leading out from the uterus. The interior of the canal is lined with tissue filled with glands that produce mucus. This is called glandular or “columnar” tissue. The end of the cervix is lined with tissue that is flat and smooth like the lining of the vagina and is, in fact, continuous with the vagina. This is called flat or “squamous” tissue. These 2 types of tissue meet at the squamo­columnar junction, which is the area where precancer and cancer are most likely to arise and therefore the area of greatest importance in a Pap test. (A sample from further inside the cervical canal is also needed.)

The squamo­columnar junction is not fixed but rather undergoes continuous changes during puberty and the childbearing years, as squamous or flat tissue slowly covers over the glandular tissue that grows out of the cervical canal. This process is called the squamous metaplasia. The squamo­columnar junction is usually found at the opening of the cervical canal (the “os”) or on the outside part of the cervix (the “portio”) during a woman's reproductive years, but often recedes up into the canal after menopause, making an accurate Pap smear difficult. For this reason, postmenopausal women are more likely to have Pap tests reported as “inadequate sample” or “unsatisfactory.”

Women whose mothers took DES while pregnant with them may have a very large area of glandular or columnar tissue on the outside of the cervix, even extending into the vagina. Some experts believe that this is the reason for the increased risk of cancer among women exposed to DES, although there is currently no definitive proof.

CANCER-PRONE ZONE WHERE VAGINA AND CERVIX MEET

The mucus-producing lining of the cervical canal (called “columnar” tissue after the shape of its outer cells) meets the surface covering of the vagina (made up of squamous epithelial cells) at a line of demarcation called the “squamo-columnar junction.” It is in this shifting zone of disparate cells that abnormal growth is most likely to arise. Central to the Pap test is an adequate sample from this important point.

A good Pap test requires more than just knowing the right tissue to sample. Your preparation and the doctor's instruments are also important, and accurate interpretation is a necessity.

Preparation

You should not douche, or use any medications or creams in your vagina or have intercourse for 24 to 48 hours prior to having a Pap test. This is because douching may remove cells, and vaginal creams and fluids from intercourse can obscure or hide cells shed from the cervix. Blood can also obscure cervical cells, so if you are menstruating and your flow is heavy, you should schedule your exam for after your period. In fact, some pathologists (doctors who specialize in analyzing tissue) recommend that a Pap test should be delayed until 14 days after your period.

Tools of the Test

A wooden spatula and Q­tip have been the usual means for collecting cells for a Pap test for many years. Recently, doctors have begun using new tools such as the cytobrush, cervix brush, and plastic spatulas because they collect more cells, providing a better sample. The major drawback is that tools with a brush­like surface are more abrasive and more likely to cause bleeding. For this reason, they are usually not used for pregnant women.

Taking the Sample

1) Your doctor will insert a tool called a speculum into your vagina using water as a lubricant if necessary; K-Y Jelly and other commercial lubricants can obscure the cells in the sample. If there is a large amount of discharge on the cervix, the doctor will gently wipe it off.

2) The next step is to scrape the outside of the cervix carefully with the spatula, rotating it 360 degrees to ensure a sample of the entire area. This sample is smeared on a glass slide in as thin a layer as possible, then quickly “fixed” by spraying or immersing it in a fixative. This preserves the cells in the state which they were found and prevents drying.

3) Next, the endocervical canal is sampled with a Q­tip or cytobrush, again rotating the tool 360 degrees to sample the entire canal. This sample is smeared on the same or a new slide, and fixed.

If you were exposed to DES before birth, your doctor may take an additional sample from the upper two­thirds of the vagina to check for vaginal cancer that could possibly result from that exposure. Some doctors also advocate taking a sample from the vagina in an effort to detect cells shed from cancers of the uterus, fallopian tubes, or ovaries. However, this is generally not necessary since it rarely provides useful information, and there are tests that better evaluate these problems.

Getting Results

The slides are sent to a laboratory for evaluation. First, the samples are stained so that the features of the cells are clear. Then they are examined by a cytologist (someone trained to review cell structure under a microscope). The cytologist's job is to identify abnormal­appearing cells among the many normal ones on the slides; every cell must be evaluated.

HOW A PAP SMEAR IS TAKEN

To gain free access to the cervix, the doctor first inserts into the vagina a device called a speculum (Step 1). With a tiny wooden or plastic spatula, the doctor then takes a scraping from the entire outer circumference of the cervix (Step 2). The cells inside the cervix must also be sampled, so the next part of the procedure calls for insertion of a Q-tip or brush into the cervical canal itself (Step 3). Finally, some doctors follow up by swabbing a cell sample from the upper two-thirds of the vagina (Step 4).

How Reliable are the Results?

The accuracy rate of the Pap test is estimated to be 80 to 90 percent. Thus, you have as much as a 1 in 5 chance that any given test will be wrong. The most likely kind of error is called a false­negative. This means that the test fails to detect a cell abnormality that is present on the cervix. Another kind of error is a false­positive, which means that the test results indicate a cell abnormality that is not actually there. The error rate seems high but there are a number of points where error may occur.

Types of Error

Patient preparation. Douching can remove abnormal cells from the cervix. Using vaginal creams or medications, or having intercourse prior to the Pap test, can introduce substances that obscure abnormal cells. Menstrual blood can also obscure the cells.

Sampling error. It is always possible, when collecting the sample, to miss an area of abnormal cells. This can occur even though your doctor is well­trained and experienced. It is called an inherent error, which means that there is no way to completely eliminate the possibility of its happening. In addition, if the sample dries before fixation (this can happen in seconds, as it is a very thin layer), or is not properly fixed, it may defeat interpretation.

Errors of interpretation. When cervical cells shed, they begin to degenerate as part of their normal life cycle. This degeneration is liable to misinterpretation during laboratory examination, resulting in a false­positive report of abnormalities. This is another source of inherent error. Also, errors can easily arise if the cytologist is not well­trained, uses poor judgment, or has inadequate time to thoroughly inspect the slide. For this reason, quality­control in cytology labs is currently a hot topic; standards for the number of slides screened per cytologist per day and unannounced tests of judgment are being reviewed and may be revised. Who should pay for the quality­control programs in this era of cutting medical costs is an equally hot topic of debate.

What To Do About Reliability

The 10 to 20 percent error rate has resulted in two important recommendations: First, if you are at increased risk for cervical cancer, you should have an annual Pap test. The likelihood of a false­negative test 2 years in a row is low. Second, if you receive an abnormal Pap test report, you should talk to your doctor about a further evaluation. A single abnormal report is not a diagnosis.

What the Report Tells You

In 1991, a new system to report Pap test results was introduced. This system, called Bethesda, gives results in a more descriptive way than previously. First, the adequacy of the sample is described and if the cytologist or pathologist notes an infection, it is described as well. If there are abnormalities in the squamous cells from the end of the cervix, they are described and attributed (if possible) to infection, inflammation, or precancerous changes. Sometimes it is not possible to classify the abnormality, so the cells are described as atypical, of undetermined significance.

Cells that appear to be undergoing a transformation to cancer are classified as either low­grade or high­grade “squamous intraepithelial lesions” (SIL). Low­grade SIL includes mildly precancerous cells and those showing signs of infection with HPV. They are grouped together because cytologists and pathologists cannot consistently distinguish between them, and because the recommendations for treatment and follow­up are usually similar. High­grade SIL includes moderately or severely precancerous cells and the condition in which the full thickness of the cervical lining contains abnormal cells (carcinoma in situ). Treatment and follow­up is the same for all of these types of lesions.

The cytologist will also describe any abnormalities in the glandular cells. With these cells, even the description of atypical is worrisome, because cancer of the glandular tissue is believed to start deep in the gland, may not shed for a long time, and may not be detected until well established. As a result, abnormal glandular cells always warrant further evaluation. Sometimes glandular cells from within the uterus (endometrial cells) are found; these may or may not warrant further evaluation, depending on where you are in your menstrual cycle, whether you've passed menopause, and whether or not the cells are described as atypical.

Interpreting the Report

If your Pap test results are anything other than normal, you should discuss them with your doctor and be prepared to take the next steps. Remember that the test does not yield a diagnosis; rather, it is a screen that suggests what the appropriate next steps should be.

Unsatisfactory or Inadequate Sample

If your results come back as unsatisfactory or inadequate, it means that the cytologist did not find enough cells on the slide to evaluate, or that no glandular cells were found. In some cases, you'll want to have a repeat test, especially if you have previously had an abnormal test or have risk factors for the abnormal cell growth called dysplasia. In other cases, your doctor may believe that he or she obtained as good a sample as possible, and that repeat testing is not necessary. This may very well be the case if you are postmenopausal and your squamo­columnar junction is high in the cervical canal. In any case, you should discuss the significance with your doctor. You should feel free to request a repeat test if you desire, even if your doctor does not feel it is necessary.

Infection

The Pap test may report Trichomonas (a sexually­transmitted vaginal infection), Candida (yeast) or large amounts of bacteria, usually Gardnerella (the most common bacteria normally found in the vagina). You can have these infections without any symptoms. Your doctor may want to do further testing which usually involves taking a sample of vaginal discharge and inspecting it under a microscope for the presence of these organisms.

Rarely, a Pap test may indicate the presence of cells that appear to be infected with the Herpes virus. Pap tests are not reliable as a test for Herpes and the results should never be offered as a definitive diagnosis. Instead, your doctor should take a culture that tests specifically for Herpes.

Reactive or Repair­related Changes

These changes are sometimes seen if you've had an infection or a recent cervical procedure, such as a biopsy. They may also be found in Pap tests from women who are postmenopausal, because the lack of estrogen that was previously produced by the ovaries can cause the vaginal and cervical lining to become very thin and inflamed (atrophic vaginitis). In addition, women who use an IUD (intrauterine device) for contraception often have reactive changes on their cervix, due to slight irritation from the IUD string. And you can get a similar irritation leading to a reactive change if you frequently use a diaphragm or cervical cap. Finally, women who have radiation treatment of the pelvis may also show reactive changes. Generally, if the cause of a reactive change is known, no further evaluation or treatment is advised. If the cause is not known, a repeat exam may be suggested.

Squamous Cell Abnormalities

Atypical squamous cells of undetermined significance means that the cytologist found cells that appear abnormal, but that the exact cause of the abnormality is not clear. If the cytologist can make this determination, the report should suggest whether the cause is more likely to be inflammation or precancer. Generally your doctor will recommend a repeat Pap test or further evaluation.

Low­grade squamous intraepithelial lesion means that cells have been found which appear to be undergoing a transformation to a state of uncontrolled growth. If the cell growth is described as low­grade, the abnormality is considered mild. In about half of these cases, the cells spontaneously revert to normal. However, there is a 25 percent chance that the abnormality may persist and another 25 percent chance that it will progress to a higher degree of abnormality, and thus to cancer. In these situations, further evaluation is always recommended.

High­grade squamous intraepithelial lesion is a discovery of cells that are moderately or severely abnormal and are undergoing a transformation to a state of uncontrolled growth. The likelihood that these cells will progress to cancer is 50 to 75 percent. If the report finds that these cells are present, the next step is a biopsy to see if the cells are, in fact, cancerous.

Cancer. If the cells readily appear to be cancer, your doctor will do a biopsy to confirm the Pap test report.

Glandular Cell Abnormalities

Endometrial cells are shed from the lining of the uterus and they can sometimes show up on a Pap test. If you were in the middle of your period during the Pap smear, this is a normal finding; even if you were not actively menstruating, endometrial cells could have been seen. There are 2 situations where endometrial cells in a Pap test may indicate a state of rapid or uncontrolled growth in the uterine lining. First, if repeated Pap tests show endometrial cells when you are not actively menstruating, and second, anytime these cells are seen on a Pap test when you are postmenopausal. In either of these cases, your doctor should suggest further evaluation with a biopsy of the lining of the uterus. Also, if the endometrial cells are described as appearing abnormal, further evaluation is warranted even if you have not reached menopause.

Atypical glandular cells of undetermined significance are glandular cells that are abnormal in appearance without an obvious cause. This is more worrisome than the same finding applied to squamous cells, because cancer arising in glandular cells can develop undetected for a long time. The cells also may have descended from high in the cervical canal, above the area normally sampled by the endocervical brush. The test report should state whether the abnormality is more likely due to inflammation or a precancerous process. Regardless, this finding should always be evaluated further with colposcopy (a visual inspection of the cervix) and endocervical curettage (scraping the cervical canal with a sharp instrument to obtain a large sample of cells).

Cancer of glandular cells. If cancer is seen in the glandular cells, your doctor will want to confirm the Pap test results.

Next Steps

If you've received an abnormal Pap test result, your doctor may recommend any one of a number of further diagnostic tests. These are covered in greater detail in chapter 38, “Cervical Cancer: The One That's Preventable.”

Colposcopy

A colposcopy is generally the first test done after an abnormal Pap test result. It is a visual inspection of the cervix using a low­power microscope.

In a colposcopy, your doctor is looking for rapidly growing areas of tissue, abnormal blood vessel patterns, or abnormal surface contour. If any of these abnormalities are seen, your doctor will take a biopsy (small pieces of tissue) and send it to a pathology laboratory for a definitive diagnosis. A diagnosis by biopsy is considered 100 percent accurate, unlike a Pap test report.

A cervical biopsy is usually painless, although some cramping may occur afterward. If you find cervical manipulation painful, ask your doctor for a local anesthetic (similar to that used in dental procedures). Endocervical curettage, or scraping the endocervical canal with a sharp instrument to obtain a large sample of glandular cells, is also often done during a colposcopy. After the biopsy, your doctor may apply medication to the cervix to stop or prevent bleeding; this may result in a dark vaginal discharge resembling coffee grounds that can last up to a week. You will be told not to use tampons, douche, or have intercourse for several days, until the biopsy sites have healed and the risk of infection has passed.

If colposcopy does not provide a view of the entire squamo­columnar junction, or show an abnormal area that extends high into the cervical canal, your gynecologist may recommend conization of the cervix. This is a minor operation in which a part of the cervix surrounding the canal, including the squamo­columnar junction, is surgically removed. It is performed in an operating room, with anesthesia and is usually done on an outpatient basis (no overnight hospitalization). A pathologist will evaluate the tissue and determine whether precancerous growth is present; if so, it has often been entirely removed, and no further treatment is necessary.

Endometrial Biopsy

If endometrial cells are reported on a Pap test in a postmenopausal woman, or on repeated Pap tests in a premenopausal woman who is not menstruating at the time of the Pap test, doctors usually recommend a biopsy of the tissue that lines the uterus. The presence of these cells in a Pap test, even if they are normal in appearance, may mean that the endometrium is growing at an abnormally rapid rate, undergoing a transformation to a state of uncontrolled growth. This transformation is called endometrial hyperplasia and is considered a precancerous state. It is important to detect and treat this condition before it becomes cancer.

If the Diagnosis Is Dysplasia

If precancerous or uncontrolled cell growth (dysplasia) is diagnosed on a cervical biopsy, your doctor will discuss the next steps with you. Mild dysplasia may be managed with observation, repeating cervical evaluation by Pap test, colposcopy, and biopsy at intervals of 3 to 6 months. Over time, mild dysplasia will either resolve on its own or progress to moderate/severe dysplasia. These forms of dysplasia should always be treated, and you and your doctor may also decide to treat a mild dysplasia right away. Methods of treatment include laser vaporization, excision with electrical loop, freezing, or conization as described above. All of these methods are considered 90 percent curative when performed properly. The 10 percent failure or recurrence rate is considered unavoidable. For this reason, follow­up is especially important. Cervical evaluation by colposcopy, Pap, or both should be carried out at 3 to 6 month intervals for 1 to 2 years after treatment.

More Good Reasons to Get Your Test

The Pap test is not perfect but it is one of the few tests available to detect precancer and therefore prevent cancer from developing. It is easy, relatively inexpensive, and can be done during a visit for contraception or other health care.

Women who avoid having a Pap for reasons of discomfort should be aware that doctors can be gentle; if yours is not, you should ask for a softer touch. If your request is disregarded, don't be afraid to find another doctor, getting a referral from a friend or local hospital.

And remember that although the Pap test has a significant error rate, the greatest error of all is to avoid having it; prevention is still the best medical care!

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