With these intervals, if an HPV infection or cell changes are missed at one screening exam, chances are good that those changes will be detected at the next one, when they can still be treated successfully
The success of cervical cancer screening is due, in part, to the repeat testing that women typically undergo over many years. A study of a large population of women receiving routine screening showed that women with a history of negative HPV/Pap cotest results have a very low risk of developing precancer or cancer even if a subsequent screening test reveals a new HPV infection or abnormal cervical cells.
For women age 30 or older, both HPV/Pap cotesting and HPV testing alone are more sensitive than Pap testing alone. It is for that reason that, when Pap and HPV cotesting or HPV testing alone are used, the recommended screening interval is 5 years: this longer interval (compared with 3 years for women receiving Pap testing alone) still allows abnormalities to be detected in time to treat them while reducing the detection of HPV infections that would be successfully controlled by the immune system.
Both Pap and HPV cotesting and HPV testing alone may also improve the detection of glandular cell abnormalities, including adenocarcinoma of the cervix (cancer of the glandular cells of the cervix). Glandular cells are mucus-producing cells found in the endocervical canal (the opening in the center of the cervix) or in the lining of the uterus. Glandular cell abnormalities and adenocarcinoma of the cervix are less common than squamous cell abnormalities and squamous cell carcinoma. Pap testing is not as good at detecting adenocarcinoma and glandular cell abnormalities as it is at detecting squamous cell abnormalities and cancers.
Likewise, HPV test results can either be “positive,” meaning that a patient’s cervical cells are infected with one or more of a group of high-risk HPV types (which is what most commercially available HPV tests detect), or “negative,” indicating that none of the high-risk HPV types were found. Several HPV tests are specific for HPV16 and HPV18-the types that cause most cervical cancers.
Therefore, a woman with a negative HPV test and normal Pap test-or just a negative HPV test-has a very low risk of developing precancerous cervical lesions over the next several years
A woman may want to ask her provider for specific information about her Pap and HPV test results and what these results mean.
Most laboratories in the United States use a standard set of terms, called the Bethesda System, to report Pap test results. Under the Bethesda System, samples that have no cell abnormalities are reported as “negative for intraepithelial lesion or malignancy.” A negative Pap test report may also note certain benign findings, such as common infections or inflammation. Pap test results also indicate whether the specimen was satisfactory or unsatisfactory for examination. Guidelines committees are re-evaluating how results of cervical screening tests are reported, based on the most up-to-date research on the natural history of HPV infections.
The Bethesda System considers abnormalities of squamous cells and glandular cells ous cell abnormalities are divided into the following categories, ranging from the mildest to the most severe.
- Atypical squamous cells (ASC) are the most common abnormal finding in Pap tests. The Bethesda System divides this category into two groups, ASC-US and ASC-H:
- ASC-US: atypical squamous cells of undetermined significance. The cells do not appear completely normal, but the cause is unclear. The changes may be related to an HPV infection, but they can also be caused by other factors.