Understanding the Pap Smear

What is a Pap smear?

The Pap smear is a screening test used to discern differences between the appearance of normal and cancerous cervical cells. The test is simple, easy-to-perform, and inexpensive, making it an ideal screening test. Developed in the early 20^th century by Dr. George Papinicolau, cells from the cervix were first obtained using a brush or spatula, placed on a slide, and viewed under a microscope.

Very little has changed over the years, except one important development: the cells are now collected in a liquid, which allows for HPV (human papilloma virus) testing. The cytology (appearance of the cells) and the HPV testing together provide a very powerful screening tool for the detection of cervical cancer and pre-cancerous lesions (dysplasia) in women. Early detection of cervical cancer offers a greater chance at successful treatment and a cure. Therefore, it is important to stay current with having routine Pap smears completed through a gynecologist.

Who needs a Pap smear, and how often should it be completed?

Pap smears are recommended for all women between the ages of 21-65. The frequency of testing depends on three key factors: age, type of screening, and history of previous abnormal results.

Age. Women of different age groups experience different health risks.
Type of screening performed. Depending on what your physician screens for, you may not need to test as frequently.
History of previous abnormal results. Women with abnormal results may be asked to screen more frequently to ensure they maintain good health.

Women aged 21-29 should receive a Pap smear every three years. This test is cytology only (examining the appearance of the sample for pre-cancerous lesions or cancerous cells), and HPV screening is not recommended in this group. The reason for this guideline is that many women in this age group tend to be positive for HPV, but their immune system clears the virus before it has a chance to do any damage. Therefore, the test is intended to screen for the primary concern: cervical cancer.

Women 30-65 should receive a Pap smear with HPV testing every five years. Special exceptions to this guideline are women with previous abnormal testing, who may require more frequent screening; women who have had a hysterectomy, who do not need further Pap screening; and women who were exposed to DES (Diethylsibestrol, a synthetic form of the female hormone estrogen, that was prescribed to pregnant women between 1940-1971 to prevent miscarriage) as a fetus, who need lifelong screening.

How do I understand my Pap smear results?

Now that you have had your Pap smear, what do the results mean? Pathologists have developed a standard system for interpreting Pap smears. This system reports the cytology results, the HPV results, and describes any additional findings. The goal is to determine who requires further testing and who can remain on a routine schedule for screening. This is based on the risk that the patient will have dysplasia (pre-cancerous cells). Here is a quick overview of Pap results and what they mean:

Normal. Cells show no evidence of pre-cancerous lesions (dysplasia), and the patient can return for routine screening.
Normal but positive for high risk HPV testing. The patient has normal cells, but is at risk for developing dysplasia, so should return in one year for another Pap and HPV test.
ASC-US. This stands for “atypical squamous cells of undetermined significance.” If this result is obtained, gynecologists then look to the HPV testing to determine the next step. If the HPV is negative, the risk of dysplasia is low and the patient may maintain a routine screening schedule. If it is positive, the patient should have a colposcopy (more on this later).
LSIL stands for “low-grade squamous intraepithelial lesion.” It represents abnormal cells, but that are likely to spontaneously resolve without treatment. These patients also receive colposcopy if the HPV testing is positive.
HSIL (high-grade), ASC-H (atypical cells, cannot rule out high-grade lesion) and AGC (atypical glandular cells) are all precancerous lesions and should receive colposcopy and other tests as indicated by the care provider.

What about HPV testing?

Several strains of high-risk HPV can be detected by the Pap smear. The presence of high-risk HPV is necessary for the development of pre-cancerous lesions (dysplasia), but the vast majority of people who are infected with the virus do not go on to get dysplasia or cervical cancer. If the test is negative, we know the risk of developing dysplasia in the next few years is low. If the test is positive, it does not mean the patient will get dysplasia. It just means we need to monitor the patient more closely while her immune system does its job of fighting the virus and preventing dysplasia.

What if my pap and HPV testing indicate I am at risk of having dysplasia?

The next step is a colposcopy. The colposcopy is a simple office procedure. Your clinician will look at your cervix directly with a microscope and perform biopsies if necessary. This test will determine if dysplasia is present, and if treatment is required to treat dysplasia and prevent the development of cervical cancer.

The big picture

The Pap smear is a powerful screening test used to detect the presence of cervical cancer or precancerous lesions. The Pap can detect these lesions years before cervical cancer develops, allowing for minimally invasive prevention of a deadly disease. This useful screening procedure is quick, relatively painless, and can save your life. Be sure to schedule your annual exam and Pap smear with your Axia Women’s Health gynecological care provider.