The Papanicolaou test, commonly known as the Pap test or Pap smear, is a routine screening procedure in women’s healthcare. This test examines cells collected from the cervix to detect changes that could indicate precancerous cells or cervical cancer. Its widespread use has significantly reduced the incidence and mortality rates associated with this type of cancer by facilitating early detection. The Pap test is routinely performed as part of a pelvic examination.
The Acronym and Its Origin
The acronym “Pap” refers to the Greek physician who developed the technique, Dr. Georgios Papanicolaou. He was a pioneer in cytology, the microscopic study of cells. His method of staining and examining exfoliated cells revolutionized the early diagnosis of cancer.
Dr. Papanicolaou began his work on this staining method in the 1920s, initially studying cellular changes in the vaginal fluid of guinea pigs. He later applied this cytological technique to human cervical cells, publishing his findings in the 1940s. The process he developed became the standardized screening tool recognized globally by his name.
Purpose and Procedure of the Screening
The primary function of the Pap test is to screen for precancerous lesions and cancer of the cervix, the lower end of the uterus. Identifying abnormal cell changes early allows healthcare providers to intervene before cancer develops or spreads. This procedure is performed during a pelvic exam and typically takes only a few minutes.
The healthcare provider inserts a speculum into the vagina to hold the walls open and visualize the cervix. A sample of cells is gently collected from the surface of the cervix and the endocervical canal using a small brush, broom, or spatula. This process gathers cells from the transformation zone, where most abnormal changes originate.
The collected cells are placed into a liquid-filled vial or smeared onto a glass slide before being sent to a laboratory for analysis by a cytotechnologist or pathologist. Modern screening often combines the Pap test with a Human Papillomavirus (HPV) test, known as co-testing, using the same sample. Testing for HPV is relevant because nearly all cervical cancer cases are caused by persistent infection with high-risk types of the virus.
Interpreting Pap Test Results
Pap test results are reported using a standardized system, most commonly the Bethesda System, which classifies findings into several categories. A “Negative for Intraepithelial Lesion or Malignancy” (NILM) result is the desired outcome, indicating that only normal cervical cells were observed. Conversely, a result may be deemed “Unsatisfactory” if the sample did not contain enough cells or was obscured by blood or inflammation, requiring a repeat test.
One common abnormal finding is Atypical Squamous Cells of Undetermined Significance (ASC-US), meaning the cells look slightly irregular but the cause is unclear. These changes are usually minor and may be related to infection or irritation, often resolving on their own. Low-Grade Squamous Intraepithelial Lesion (LSIL) is a more specific finding, suggesting mild cellular changes typically caused by an HPV infection.
High-Grade Squamous Intraepithelial Lesion (HSIL) indicates significant cellular abnormalities considered precancerous. These cells are severely abnormal and are less likely to resolve naturally compared to LSIL, carrying a higher risk of progressing to invasive cancer if left untreated. The result may also indicate Atypical Glandular Cells (AGC), meaning the cells lining the inner cervix or uterus appear irregular and require further investigation.
Follow-Up Steps After Abnormal Findings
Receiving an abnormal Pap test result does not mean an individual has cancer, but follow-up is necessary to clarify the finding and prevent disease progression. The specific next step depends on the classification of the abnormal cells and whether a concurrent HPV test was positive. For minor changes like ASC-US with a negative HPV result, a healthcare provider may recommend a repeat Pap test in three to five years.
If the result is ASC-US with a positive HPV test, LSIL, or HSIL, the patient is typically referred for a colposcopy. During this procedure, the doctor uses a magnifying instrument to examine the cervix closely, often applying a vinegar-like solution to highlight abnormal areas. If suspicious tissue is observed, a small tissue sample (biopsy) will be taken for definitive diagnosis.
Follow-up procedures based on the biopsy results range from continued monitoring for low-grade lesions to treatment for high-grade lesions. Treatment usually involves procedures like the Loop Electrosurgical Excision Procedure (LEEP) or cryotherapy, which remove or destroy the abnormal cells. These preventative steps are highly effective and are why regular screening has dramatically improved outcomes.