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Screening for cervical cancer

The most important risk factor for developing cervical cancer is infection of the cervix with human papillomavirus (HPV). HPV is spread mainly through sexual contact (including sexual intercourse, genital skin-to-skin contact and oral sex), and the virus can appear years after you have been exposed to it. Using a condom during sex may decrease the chance that you will pick up HPV, but a condom can only provide partial protection as it doesn’t cover the entire genital area.

Even if you’ve had the HPV vaccine, regular Pap tests are still needed. The HPV vaccine doesn’t protect against all types of HPV.

  • Our recommendation

    If you’ve ever been sexually active, you should start having regular Pap tests by the time you’re 21. You’ll need a Pap test every 1 to 3 years, depending on your previous test results. Even if you have stopped having sex, you should continue to have a Pap test. If you’ve had a hysterectomy, you may still need a Pap test, but talk to your doctor about whether this is necessary.

  • The Pap test

    A Pap test is a quick and simple test used to look for any changes in the cells of the cervix. It’s done in your doctor’s office and though it can be uncomfortable, it shouldn’t be painful.

    Preparing for your test

    Try to schedule your Pap test for the middle of your menstrual cycle – between 10 and 20 days after the first day of your period.

    For 48 hours before your Pap test:

    • Avoid vaginal douching.
    • Don’t use any vaginal medications or contraceptive (spermicidal) creams, foams or jellies (except as directed by your physician), as these may wash away or hide abnormal cells.

    For 24 hours before your Pap test:

    • Avoid having sex.
    At your doctor’s office

    Your doctor will use a small wooden spatula to gently scrape the surface of the lower part of the cervix to pick up cells. A special brush called a cytobrush is used to obtain cells from the upper part of the cervix that leads into the uterus. The cells are then smeared onto a glass slide and the sample is sent to the laboratory where they’re examined under a microscope. If the screening test shows a change or abnormality, follow-up tests may be done. They could include:

    • another Pap test
    • an HPV test
    • colposcopy
    • biopsy

    Most abnormal Pap tests result from precancerous changes, which can be easily detected and treated successfully. Most precancerous changes result from cervical HPV infection. These changes are not cancer and are also known as dysplasia.

  • What is dysplasia?

    Dysplasia of the cervix is not cancer. It is a precancerous change that may develop into cancer if it isn’t treated. Dysplasia of the cervix means that abnormal changes have taken place in the cells of the cervix. It is usually picked up during your routine Pap test.

    Dysplasia of the cervix is also known as:

    • SIL (squamous intraepithelial lesion)
    • CIN (cervical intraepithelial neoplasia)

    The most advanced form of CIN (CIN 3) is actually the very earliest form of cancer. Ask your doctor to explain the terms that apply to your diagnosis.

    Dysplasia is quite common and should not alarm you, as it can be easily treated. Treatments for dysplasia may include:

    • laser surgery
    • electrosurgery (also called LEEP or LLETZ)
    • cryosurgery
    • surgery
  • Benefits and risks of screening

    Almost every test or procedure has benefits and risks. It’s important to be aware of them so that you can make an informed decision that’s right for you. No screening test is 100% accurate, but the scientific evidence tells us that having Pap tests leads to a decrease in death rates in women with cancer.

    • Early detection of precancerous cervical changes: Cervical cancer develops from precancerous cervical changes. Screening helps identify these changes early so they can be treated or watched, preventing cervical cancer from developing.
    • Better survival rates: The Pap test can help detect (find) early stage cervical cancer. In most cases, the earlier a cancer is detected, the better your chance of survival.
    • Better quality of life: Early detection may also mean less treatment and less time spent recovering.
    • Women who are not screened or not screened regularly have a higher risk of developing cervical cancer.
    • False-positive results: This happens when test results suggest cervical abnormalities such as precancerous cervical changes even though cancer is not present. False positives can cause anxiety, stress and possibly painful and unnecessary tests to rule out precancer or cancer (that is, to make sure you don’t have cancer when the screening test has suggested you might).
    • False-negative results: This happens when cervical cell abnormalities are not detected by the test even though they are present. False-negative results can cause you or your doctor to be unaware of cervical abnormalities that could lead to cancer or to ignore symptoms that suggest the presence of cancer, causing a delay in diagnosis and treatment.
    • Unnecessary follow-up procedures or treatment: Some women with cervical abnormalities may have follow-up procedures or treatment for a condition that may never have developed into cancer. Cervical abnormalities in many young women often go away on their own without treatment (if they are the low-risk kind). Follow-up procedures or treatment (for example, removal of lesions) may result in complications or affect reproductive health.


Dr Shawn Li I’m extremely grateful to the Canadian Cancer Society for funding my research with an Innovation Grant.

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