A smear test, also known as a Pap test or Pap smear, is a routine screening procedure used to detect potentially precancerous and cancerous processes in the cervix. It is an important tool to detect cervical cancer in its early stages when treatment is most effective. However, a common question many women have is whether a normal Pap smear result guarantees that they do not have cervical cancer or other gynecological cancers. Below we will examine what exactly a Pap smear screens for, its limitations, and other screening options available.
What a Pap Smear Screens For
A Pap smear is designed to identify precancerous changes and cancerous cells from the cervix, the lower, narrow part of the uterus that connects to the vagina. During a Pap smear, a sample of cells is collected from the cervix using a small brush and spatula. The cells are examined under a microscope to look for abnormalities that could signal cervical cancer or conditions that can lead to cervical cancer if left untreated.
Specifically, the Pap smear screens for:
- Cellular changes called dysplasia that can range from mild (LSIL or low-grade squamous intraepithelial lesion) to more severe (HSIL or high-grade squamous intraepithelial lesion). LSIL changes often resolve without treatment, while HSIL indicates precancer that requires further testing and possible treatment.
- Cancerous cells, signaling invasive cervical cancer
- Inflammation and/or infection
By detecting abnormal precancerous changes, cervical cancer can be prevented by treating these cellular abnormalities before actual cancer develops. The Pap smear has helped dramatically decrease rates of cervical cancer incidence and mortality since its widespread implementation.
However, it is important to keep in mind the Pap smear only screens for cervical abnormalities and cancer. It does not screen for other gynecological cancers or cancers elsewhere in the body.
Limitations of the Pap Smear
While an effective and widely used screening tool, the Pap smear does have its limitations:
- Not 100% accurate – Can produce false negatives where abnormal cells are missed as well as false positives where normal cells appear abnormal. The false negative rate is estimated to be about 20-30%.
- Does not detect all cervical abnormalities or cancer – Some abnormal tissue or cancerous cells may be missed by the sampling and require additional testing.
- Does not detect ovarian, uterine, vaginal, or other cancers – as it only examines cells from the cervix.
- May be affected by sample collection and preparation – Inadequate cell sampling or errors preparing the slide can lead to incorrect test results.
- Human error – Abnormalities may be missed if the slide is not examined correctly under the microscope.
For these reasons, while the Pap smear is an invaluable screening tool, it is not perfect and should be used in conjunction with other screening approaches as recommended by your healthcare provider.
Other Cancers and Conditions Not Detected by a Pap Smear
It is important for patients to understand that a normal Pap smear result does not indicate a clean bill of health or absence of other cancers and gynecological conditions beyond cervical cancer. Cancers and precancers that are not detected by a Pap smear include:
- Uterine/Endometrial Cancer – Cancer of the lining of the uterus. Most common gynecologic cancer in developed countries.
- Ovarian Cancer – Cancer of the ovaries. Often called a “silent disease” with nonspecific symptoms in early stages.
- Vaginal Cancer – A rare cancer of the vagina itself.
- Vulvar Cancer – Cancer of the vulva or external female genitalia.
- Uterine or Ovarian Precancers – Such as complex atypical hyperplasia of the endometrium or borderline ovarian tumors.
- Chronic Pelvic Pain – Pain in the pelvic region lasting >6 months that can result from many causes including endometriosis, pelvic inflammatory disease, uterine fibroids, irritable bowel syndrome, and more.
- Polycystic Ovary Syndrome (PCOS) – A hormonal disorder causing enlargement of the ovaries with small cysts on the outer edges. Can lead to abnormal bleeding, infertility, and other health problems.
While some of these conditions may produce abnormalities detected on a Pap smear if they involve the cervix, they originate outside the cervix and would require other diagnostic testing. A normal Pap smear does not rule out any of these other problems.
Who Should Receive Routine Pap Smears
Current guidelines from the American Cancer Society recommend the following for routine Pap smear screening:
- Women ages 21-29 should have a Pap smear every 3 years.
- Women ages 30-65 can have a Pap smear every 3 years, a Pap smear plus HPV test every 5 years, or HPV testing alone every 5 years.
- Women over 65 may stop screening if they have had adequate prior screening with normal results.
- Screening should continue for certain women with risk factors such as suppressed immune systems, prior abnormal Pap results, or DES exposure before birth.
Ideally, women should have two normal Pap smear screens in a row before moving to less frequent testing every 3-5 years. Testing should stop at age 65 with an adequate negative screening history. Women who have had a total hysterectomy for non-cancer reasons may also be advised to discontinue Pap smears. However, those who have had a hysterectomy that removed the cervix should continue with screenings until age 65.
In addition to routine Pap smears, your doctor may recommend additional testing at certain ages or if any symptoms warrant further evaluation. Do not hesitate to discuss any abnormal bleeding, pelvic pain, or other issues with your healthcare provider.
Additional Cancer Screening Tests for Women
Along with routine Pap smears, women should also discuss implementing these recommended screening tests with their doctor:
HPV Testing
HPV (Human Papillomavirus) testing looks for the virus that causes nearly all cases of cervical cancer. It can be used in conjunction with the Pap smear for women 30-65 years old. HPV testing is often reflexively performed on Pap samples showing abnormal cells to look for the strains most likely to lead to cervical cancer.
Mammograms
Annual or biennial mammography screening detects breast cancer. Women at average risk should begin yearly mammogram screening at age 40. Those with added risk may start earlier.
Clinical Breast Exams
A physical breast exam by a medical provider during regular check-ups or well-woman visits. Helps detect lumps, swelling, skin changes, or discharge the patient may not have noticed. Should be done every 1-3 years for women in their 20s and 30s, then annually after age 40.
CA-125 Blood Test
This blood test detects levels of the protein CA-125, which may be elevated in ovarian cancer. Approved to monitor ovarian cancer treatment, it has not been found an effective screening tool for ovarian cancer in average risk women due to false positives leading to unnecessary surgery. It may be used in high-risk patients.
Transvaginal Ultrasound
An ultrasound probe is inserted in the vagina to obtain detailed images of the uterus, ovaries, and other pelvic organs. May be used to assess abnormal uterine bleeding or pelvic pain. Has not proven effective for routine ovarian cancer screening.
Endometrial Biopsy
Removes a tissue sample from the lining of the uterus to detect precancer or cancer cells. Used for women with abnormal uterine bleeding or at high risk of uterine cancer.
Colonoscopy
Visualizes the entire colon and rectum to detect colon cancer and precancerous polyps. Recommended every 10 years starting at age 45 for average risk women. Those with family history may start screenings earlier and require them more frequently.
Discuss your family history and individual cancer risks with your doctor to determine appropriate screening schedules. While tests like mammograms and colonoscopies may seem invasive or uncomfortable, they are vitally important in detecting cancers early when they are most treatable.
Conclusions
In summary:
- A Pap smear is an important screening tool designed to detect cervical cancer and precancerous changes.
- However, it does not detect all gynecological or other cancers a woman could develop.
- A normal Pap smear is not a guarantee that other serious conditions are not present.
- Women should continue routine Pap smear screenings as recommended based on their age and risk factors.
- Additional screening tests such as HPV testing, mammograms, clinical breast exams, ultrasounds, and more may be warranted.
- Discuss all screening options with your doctor to ensure early detection of any cancers or gynecological conditions.
While tremendous progress has been made in cervical cancer prevention through the use of the Pap smear, women should not rely on this test alone. Being aware of recommended guidelines and discussing them with your doctor is key to optimal well-woman care and prevention.