Screening of cervical cancer is unique in that it can prevent further development by treating pre-invasive stages. Well-organized screening programs can reduce both the incidence and mortality of cervical cancer. In Norway the incidence of cervical cancer is reduced by 25 % and mortality by 50 % since the national screening program was introduced in 1995. Cervical cancer screening has led to a decrease in incidence of cervical cancer by 60–70 %. A cervical smear is taken every three years on women between 25-69 years in the Norwegian Cevical Cancer Screening Program.
The sensitivity of a cervical smear is relatively low (55–80 %), but the specificity is high. This means that a negative test will not exclude pre-stages of cancer or invasive cancer. Cytology testing should never be the only diagnostic tool in patients with symptoms. With a positive cytological diagnosis, a histological test will show the equivalent or a more serious diagnosis in 80–90 % of cases.
A cervical sample can be taken as a conventional smear or as fluid-based cytology. Fluid-based cytology is now the preferred method. The method allows HPV testing on the same sample and enables HPV testing as a primary screening method in the future.
The quality of the sample depends more on the technique of the practitioner than on the devices used for collection. It is important to read the instructions carefully. Incorrect specimen collection is a frequent cause of false negative tests.
- Screening of healthy women without symptoms as part of the national screening program. This method should not be used as a diagnostic tool for cervical cancer.
- To obtain an adequate sample for diagnosing pre-stages of cervical cancer.
Factors resulting in poor testing:
- Postmenopausal women with atrophic mucosa
Postpone the test:
- If the patient is menstruating.
- If the patient has used vaginal cream or a diaphragm in the last 24 hours.