A Pap smear is a routine screening tool used to detect abnormal changes in the cells of the cervix, the lower part of the uterus that opens into the vagina. This test is designed to find potential cell changes before they can develop into cervical cancer. Receiving an abnormal result means cells were found that do not look entirely normal, prompting the need for further investigation. A common concern is whether this result automatically signals the presence of Human Papillomavirus (HPV).
Interpreting Abnormal Pap Smear Results
When a Pap smear is reported as abnormal, the results are categorized using specific terminology that indicates the degree of cellular change observed. The mildest and most common abnormal finding is Atypical Squamous Cells of Undetermined Significance (ASCUS). This result means the cells do not look entirely normal, but the cause cannot be definitively identified from the sample alone.
More defined abnormalities fall under the category of Squamous Intraepithelial Lesions (SIL), which are further divided by severity. Low-Grade Squamous Intraepithelial Lesion (LSIL) suggests mild changes, often referred to as mild dysplasia, that commonly resolve on their own. High-Grade Squamous Intraepithelial Lesion (HSIL) indicates more significant abnormalities that have a higher potential to progress to cancer if left untreated. Understanding these classifications confirms that an “abnormal” result describes the appearance of the cells.
The Direct Link Between HPV and Cell Changes
The Human Papillomavirus (HPV) is the most frequent cause of the cellular changes detected by an abnormal Pap smear. HPV is a common sexually transmitted infection, and certain high-risk strains are responsible for nearly all cases of cervical cancer. These strains, such as HPV 16 and 18, integrate into the host cells and interfere with the cell’s normal growth regulation.
The virus causes the cells to mutate and display the abnormal characteristics seen during a Pap test. For instance, an LSIL result almost always indicates the presence of an HPV infection. High-risk HPV is detected in a substantial percentage of abnormal Pap smears, ranging from approximately 45% in ASCUS results to over 86% in HSIL results.
When an ASCUS result is found, a reflex HPV test is performed on the same sample to check for the presence of the high-risk virus. This HPV testing helps determine the level of risk and guides the management plan. While most abnormal Pap smears are linked to HPV, most infections and resulting cell changes are temporary and clear up naturally, particularly in younger individuals.
Non-HPV Causes of Abnormal Results
While HPV is the predominant cause, an abnormal Pap smear does not guarantee an HPV infection, as other benign factors can alter the appearance of cervical cells. Inflammation of the cervix (cervicitis) caused by common infections can lead to an abnormal reading. Infections like yeast infections, bacterial vaginosis, or trichomoniasis can cause irritation that makes the cervical cells appear slightly atypical.
Changes in hormone levels, such as those occurring during pregnancy or menopause, can also affect the cell morphology seen on the Pap test. These non-HPV-related changes are associated with the mildest abnormality, such as ASCUS, and are not related to precancerous conditions. Follow-up testing helps distinguish these temporary changes from those caused by persistent high-risk HPV.
Required Follow-Up Testing and Procedures
After an abnormal Pap smear, the required follow-up is determined by the specific classification of the abnormality, the patient’s HPV status, and age. For mild abnormalities like ASCUS that test negative for high-risk HPV, or for some LSIL results, the plan is conservative. This often involves a repeat Pap or HPV test in six to twelve months, allowing time for the body’s immune system to clear the infection and for the cells to return to normal.
For more significant findings, such as HSIL or certain ASCUS results that test positive for high-risk HPV, a colposcopy is recommended. During this procedure, the healthcare provider uses a magnifying instrument to closely examine the cervix. A solution is applied to the cervix to highlight any abnormal areas, making them easier to identify.
If suspicious areas are observed during the colposcopy, a small tissue sample (biopsy) is taken for detailed laboratory analysis. The biopsy results provide a definitive diagnosis of the severity of the cell changes. This diagnosis determines whether treatment, such as the removal of the affected tissue, is necessary to prevent the progression to cancer.