Receiving a notice about an abnormal Pap smear often leads to concern about a human papillomavirus (HPV) infection. While HPV is the primary cause of significant cell changes, an abnormal Pap result does not automatically confirm the presence of the virus or a serious condition. This information clarifies the relationship between an abnormal Pap smear and HPV, explaining the factors that influence the result and outlining the terminology used by healthcare providers. Understanding the distinct roles of the two main screening tests and the meanings of the results can help prepare for the next steps in care.
Understanding the Differences Between Pap and HPV Tests
The Pap test and the HPV test serve distinct yet complementary purposes in screening for cervical cancer. The Pap test, also known as cytology, looks for abnormal changes in the cells collected from the cervix. This analysis focuses on the morphology, or appearance, of the cells to identify precancerous changes or early signs of cancer. An abnormal Pap result simply means the cells appeared unusual or atypical when examined under a microscope.
In contrast, the HPV test is a virological assessment that specifically looks for the genetic material (DNA) of high-risk strains of the human papillomavirus. High-risk HPV causes nearly all cervical cancers, so its presence indicates a risk for future cell changes. These two tests are often performed together, known as co-testing, using the same sample for a comprehensive risk assessment. The key distinction is that the Pap test detects the effect (cell changes), while the HPV test detects the cause (the virus).
Causes of Abnormal Cell Changes Beyond HPV
While high-risk HPV is the most common reason for persistent abnormalities, an abnormal Pap smear can frequently be caused by factors unrelated to the virus. Many minor cellular changes are reactive, meaning they are temporary responses to irritation or inflammation rather than true precancerous changes. The most common abnormal finding, Atypical Squamous Cells of Undetermined Significance (ASC-US), is often the result of these non-HPV factors.
Common benign causes include reproductive tract infections, such as yeast infections, bacterial vaginosis, or trichomoniasis. These infections cause inflammation, which temporarily alters the appearance of cervical cells, leading to an abnormal reading. Hormonal fluctuations, such as those during pregnancy or menopause, can also affect cervical cells and be reported as atypical. Treating the underlying infection or addressing the hormonal shift often results in a normal Pap smear upon retesting.
Interpreting Abnormal Results Terminology
Abnormal Pap results are categorized using specific terminology that indicates the degree of cell change and the potential risk level.
Atypical Squamous Cells of Undetermined Significance (ASC-US)
This is the least concerning category, meaning the cells look slightly irregular, but the pathologist cannot definitively determine the cause. If ASC-US is found, a reflex HPV test is often performed on the same sample to check for high-risk HPV. If the HPV test is negative, the risk is low.
Low-Grade Squamous Intraepithelial Lesion (LSIL)
LSIL represents mild cell changes, or mild dysplasia, typically associated with an active HPV infection. LSIL changes have a high likelihood of resolving spontaneously as the body’s immune system clears the virus over time.
High-Grade Squamous Intraepithelial Lesion (HSIL)
The most significant categories are High-Grade Squamous Intraepithelial Lesion (HSIL) and Atypical Squamous Cells that cannot exclude HSIL (ASC-H). HSIL indicates moderately or severely abnormal cell changes, suggesting a greater risk of progression to cancer if left untreated. These findings are more strongly predictive of a persistent high-risk HPV infection than LSIL or ASC-US. While all these terms describe precancerous changes, they represent a spectrum from minor and likely transient to more significant and potentially progressive.
Next Steps for Follow-Up and Management
The management protocol following an abnormal Pap smear is risk-based, depending on the severity of the cell changes and the presence of high-risk HPV. For minor abnormalities like ASC-US with a negative HPV result, or for LSIL in younger patients, the approach is often surveillance or “watchful waiting.” This involves repeating the Pap or co-test within 6 to 12 months, relying on the immune system to clear the infection and resolve the cell changes naturally.
If the result is persistent or categorized as HSIL, the next step is typically a colposcopy. This procedure allows the clinician to examine the cervix under magnification. During a colposcopy, a mild solution is applied to highlight abnormal areas, and a small tissue sample (biopsy) is taken for a definitive diagnosis.
If the biopsy confirms high-grade precancerous cells, a minor treatment procedure is performed to remove the abnormal tissue and prevent progression to cancer. Common preventative treatments include the Loop Electrosurgical Excision Procedure (LEEP) or cryotherapy, which are highly effective at removing the affected cells. The screening and follow-up system is designed to detect and treat these cell changes long before they develop into cancer, which is why cervical cancer is largely preventable.