The Papanicolaou test, commonly known as the Pap smear, is a medical screening procedure that has significantly reduced the incidence of cervical cancer. This test involves collecting cells from the cervix to examine them for abnormal changes that could indicate a precancerous or cancerous process. The Pap test is a widely used public health tool because it allows healthcare providers to identify cell abnormalities at a stage when intervention is most effective.
The Purpose of the Papanicolaou Test
The primary function of the Pap test is to screen for potentially precancerous or cancerous changes in the cells of the cervix. By detecting these cellular abnormalities, known as dysplasia or squamous intraepithelial lesions (SILs), the test provides an opportunity for early treatment before cancer can fully develop.
The development of most cervical cancers is linked to persistent infection with high-risk types of the human papillomavirus (HPV). While the Pap test looks for changes in the cells themselves, a separate HPV test looks specifically for the presence of the virus that causes those changes. Often, the two tests are performed together, known as co-testing, to provide a more comprehensive assessment of cervical health.
Identifying these cell changes early is important because the progression from HPV infection to precancerous lesions, and eventually to cancer, typically takes many years. Finding these abnormalities before they become malignant significantly increases the likelihood of a successful outcome.
What Happens During the Procedure
The Pap test is generally performed during a routine pelvic examination and usually takes only a few minutes to complete. The procedure begins with the patient lying on an examination table, often with their feet resting in stirrups. The healthcare professional then gently inserts a speculum, which is a plastic or metal instrument, into the vagina.
The speculum is slowly opened to widen the vaginal walls, allowing the provider a clear view of the cervix. The next step involves collecting a sample of cells from the surface of the cervix, specifically from the area known as the transformation zone. This collection is done using a small brush, a spatula, or a cotton-tipped swab.
The process of cell collection is quick and may cause a sensation of pressure or a minor cramp, but it is generally not painful. After the cells are collected, the sample is immediately placed into a liquid solution or a small jar to preserve them. This method, called liquid-based cytology, ensures the cells are protected for laboratory analysis. The sample is then sent to a laboratory where trained cytotechnologists examine the cells under a microscope for any signs of abnormality.
Interpreting Pap Test Results and Next Steps
Pap test results are categorized to indicate whether the collected cells appear normal or show signs of change. The most favorable result is “Negative for intraepithelial lesion or malignancy,” which means no concerning cell changes were found. If a result is negative, the person can follow the standard screening schedule recommended by their healthcare provider.
An abnormal result indicates that some cells collected from the cervix did not appear normal under the microscope, but this finding rarely means cancer is present.
Common Abnormal Findings
One common abnormal finding is Atypical Squamous Cells of Undetermined Significance (ASC-US), where the cells look slightly irregular but the cause is not immediately clear. Low-Grade Squamous Intraepithelial Lesion (LSIL) suggests mild abnormalities, which are often caused by HPV and may resolve without intervention.
More concerning findings include High-Grade Squamous Intraepithelial Lesion (HSIL), which indicates moderately or severely abnormal cells that are more likely to progress to cancer if left untreated. Another category is Atypical Squamous Cells, Cannot Exclude HSIL (ASC-H), which suggests a possibility of high-grade changes.
Follow-up Procedures
When an abnormal result is received, the next steps depend on the degree of abnormality and whether an HPV test was also performed. For less severe results like ASC-US, follow-up often involves testing the sample for high-risk HPV types, or repeating the Pap test in six to twelve months.
If the HPV test is positive, or if the Pap test shows persistent abnormalities, a referral for a colposcopy is often recommended. A colposcopy is a procedure where a healthcare professional uses a specialized magnifying instrument to closely examine the cervix.
During a colposcopy, the provider may take a small tissue sample, called a biopsy, from any areas that look irregular for further testing. For more significant findings like HSIL, a colposcopy and biopsy are typically the immediate next steps to confirm the diagnosis and plan necessary treatment. The goal of all follow-up procedures is to prevent precancerous lesions from advancing to invasive cancer.