Screening for cervical cancer
The Pap test has been the usual way to screen for cervical cancer for many years. The Pap test is used to find abnormal changes in the appearance of cervical cells. Abnormal changes are present in women with increased risk of cervical cancer.
Human Papilloma Virus (HPV) is necessary for the development of cervical cancer. Apart from the conventional Pap test, there are now two new methods of screening for cervical cancer. One is the ThinPrep method which, like the Pap test, looks for abnormal cells. Cells are taken for the ThinPrep at exactly the same time as the conventional Pap smear. After smearing the cells on the slide to make the Pap test, the spatula is rinsed in fluid and the extra cells collected for the ThinPrep test. The ThinPrep fluid is put through a special filter which removes contaminants (such as inflammatory cells, blood or mucous). In some women therefore, ThinPrep samples can be easier to interpret than Pap smears, and can reduce the number of unsatisfactory tests. This may prevent the necessity for a repeat sample. The ThinPrep
test is not Medicare refundable.
The other test is the QIAGEN Digene HPV test which is a very sensitive method of testing for HPV in cervical cells. This test detects the DNA of the virus and does not rely on changes in cell appearance. This test can be performed on the ThinPrep fluid, or a separate sample can be taken from the cervix at the same time as the Pap smear. In some instances, the HPV test is Medicare refundable (please ask your doctor for advice).
What is HPV (Human Papilloma Virus)?
HPV is detected in almost all cervical cancers. There are about 100 different types of HPV. Some types infect the skin (common warts) and others infect the anogenital area, including the cervix. Thirteen HPV types are called “high-risk” because these types are the ones which may lead to cancer. There are other types of HPV which infect the cervix but they are not associated with cancer (low-risk types). These low risk types can cause genital warts.
In most people the immune system combats the HPV infection, including the “high-risk” HPV types and removes the virus from the body. Usually this happens without any symptoms and so most people are not aware that they have ever been infected with HPV. Most women infected with HPV will not develop cervical cancer or the precancerous forms of the disease. However, if high-risk HPV infection remains over many years, there is a greater chance of developing cell changes which may lead to cervical cancer.
Who can get an HPV infection of the cervix?
HPV is a very common infection and is transmitted sexually. The majority of people who have ever been sexually active will have been exposed to the virus. However, very few women progress to cervical cancer.
What are the symptoms of HPV infection?
In most cases, HPV is harmless and does not cause symptoms. Usually, a woman only discovers that she has HPV on cervical screening, since cell changes due to HPV infection can be recognised on Pap smear. These cellular changes can occur weeks, months or many years after initial infection. However, two-thirds of young women with HPV infection do not have an abnormal Pap smear since the infection is transient.
What is the difference between the ThinPrep test, the QIAGEN Digene HPV test and the Pap test?
All tests are designed to detect women who are at increased risk of cervical cancer. These women can then be treated before a cancer develops.
The Pap test and the ThinPrep test are similar and used to recognise abnormal cellular appearances, which may be due to HPV infection or due to pre-cancerous or cancerous changes in a cell. The ThinPrep Test has the advantage of removing contaminants which interfere with the interpretation of the cervical cells, reducing the number of unsatisfactory or uncertain results. Also, since the sample is placed directly in fluid, other tests can be performed on the single sample, as required by your doctor, including the QIAGEN Digene HPV test.
The QIAGEN Digene HPV test detects high risk HPV in a cervical sample directly and does not rely on detecting abnormal cell appearances. The Digene HPV test directly identifies infection of any of the high risk HPV types.
How is the specimen collected for ThinPrep and QIAGEN Digene HPV test?
Both of these new tests are obtained from the cervix in the same manner as collecting a sample for a Pap smear and can be done at the same time or on a separate visit. Cells are brushed off the cervix and sent to the laboratory for analysis by a pathologist. The same sample collected for ThinPrep analysis may be used for the QIAGEN Digene HPV test, or a dedicated Digene sampler can be used. Neither ThinPrep nor the QIAGEN Digene HPV test can be done on the same sample as the Pap smear. A report will then be issued to your doctor.
The ThinPrep and QIAGEN Digene HPV test may reduce the uncertainty and anxiety caused by abnormal or inconclusive Pap test results. They are very useful ways to discover if you may be at increased risk of developing cervical precancer or rarely, cancer, enabling your doctor to monitor you more closely.
Both tests may prevent delays in receiving further, appropriate investigation and management if your Pap test is mildly abnormal.
What happens after I have been tested?
The results of your tests will be used by your doctor to decide whether you need:
- further investigations by a gynaecologist. These investigations usually include colposcopy, in which the gynaecologist looks directly at the cervix and may take a tissue sample for histology.
- repeat screening before two years
- whether you do not need to have anything other than the usual screening.
Why test for cervical cancer?
Before a cancer develops in the cervix, the cells become abnormal (pre-cancerous). These pre-cancerous cells can be detected by the Pap or ThinPrep tests and the abnormal cells treated. Treatment at this time will prevent cervical cancer developing, which could save your life.
The HPV test directly detects the virus which causes cervical cancer. It is a very sensitive method for detecting HPV. An HPV test can help to determine the best cause of action if the Pap and ThinPrep tests are inconclusive. A Pap test with the HPV test is recommended for patients who have been previously treated for high grade cervical lesions, since the combined tests give the most accurate assessment of whether the cancer-causing virus has been removed.
Do I still need to be screened for cervical cancer if I have been vaccinated?
Yes you do. HPV vaccines greatly reduce the chances of infection with the most cancer-causing HPV types (16 and 18), with >90% protection. However, since this vaccination cannot prevent all forms of cervical cancer, screening is still recommended.
Mater Pathology offers a comprehensive diagnostic service for women's health issues, including these three cervical cancer tests. All these tests are performed on site by skilled scientists and pathologists at Mater Pathology's South Brisbane laboratory.
You can download this brochure as a PDF by clicking this link.
24-hour collection service
Mater Private Emergency Care Centre
301 Vulture Street
South Brisbane
www.mater.org.au/pathology
Phone: 07 3163 8500