The Bethesda System (TBS)

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The Bethesda System (TBS)

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The Bethesda system (TBS) of classifying Pap tests was developed by the United States National Cancer Institute (NCI) to provide more detailed information about Pap test results. It is also used in most parts of Canada. When lab specialists examine cervical cells, they use this system to report the lab results to doctors.

Your doctor receives the report from the lab. The report tells your doctor if the cell sample taken during the examination was good enough to be evaluated. It also lets your doctor know if the cells were normal or abnormal or if there was an infection present.

If the cells were abnormal, they are put in categories, or typed, based on how severe the problem is:

  • Cells that show minor changes but the cause is unknown may be typed as ASC-US (atypical squamous cells of undetermined significance), ASC-H (atypical squamous cells that cannot exclude high-grade squamous intraepithelial lesion), or AGC (atypical glandular cells).
  • Cells that show definite minor changes but aren’t likely to become cancer may be typed as LSIL (low-grade squamous intraepithelial lesions).
  • Cell changes that are more severe and are more likely to become cancer may be typed as HSIL (high-grade squamous intraepithelial lesions).

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By Healthwise Staff
Primary Medical Reviewer Sarah Marshall, MD - Family Medicine
Primary Medical Reviewer Brian D. O'Brien, MD - Internal Medicine
Specialist Medical Reviewer Kirtly Jones, MD, MD - Obstetrics and Gynecology
Last Revised February 16, 2011

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