Pap Test - Results

Results

In screening a general or low-risk population, most Pap results are normal.

In the United States, about 2–3 million abnormal Pap smear results are found each year. Most abnormal results are mildly abnormal (ASC-US (typically 2–5% of Pap results) or low-grade squamous intraepithelial lesion (LSIL) (about 2% of results)), indicating HPV infection. Although most low-grade cervical dysplasias spontaneously regress without ever leading to cervical cancer, dysplasia can serve as an indication that increased vigilance is needed.

In a typical scenario, about 0.5% of Pap results are high-grade SIL (HSIL), and less than 0.5% of results indicate cancer; 0.2 to 0.8% of results indicate Atypical Glandular Cells of Undetermined Significance (AGC-NOS).

As liquid based preparations (LBPs) become a common medium for testing, atypical result rates have increased. The median rate for all preparations with low-grade squamous intraepithelial lesions using LBPs was 2.9% compared with a 2003 median rate of 2.1%. Rates for high-grade squamous intraepithelial lesions (median, 0.5%) and atypical squamous cells have changed little.

Abnormal results are reported according to the Bethesda system. They include:

• Squamous cell abnormalities (SIL)
  • Atypical squamous cells of undetermined significance (ASC-US)
  • Low-grade squamous intraepithelial lesion (LGSIL or LSIL)
  • Atypical squamous cells – cannot exclude HSIL (ASC-H)
  • High-grade squamous intraepithelial lesion (HGSIL or HSIL)
  • Squamous cell carcinoma

• Glandular epithelial cell abnormalities
  • Atypical Glandular Cells not otherwise specified (AGC or AGC-NOS)

Endocervical and endometrial abnormalities can also be detected, as can a number of infectious processes, including yeast, herpes simplex virus and trichomoniasis. However it is not very sensitive at detecting these infections, so absence of detection on a Pap does not mean absence of the infection.