The 2001 Bethesda System does not include guidelines for clinical management of cases in which abnormal results are found. However, the system serves as the basis for new management guidelines that appear in a companion article in the same issue of the journal. The clinical guidelines were developed under the sponsorship of the American Society for Colposcopy and Cervical Pathology in tandem with the work done to create the 2001 Bethesda System.

Publication of the two papers is considered a milestone in efforts to improve cervical cancer screening. "Together, Bethesda 2001 and the Society guidelines should provide more uniform, evidence-based care of women with cervical abnormalities," said Diane Solomon, M.D., who coordinated development of The Bethesda System at the
National Cancer Institute.

Bethesda 2001 updates the earlier Bethesda System, first published in 1989 and revised in 1991. The 2001 version reflects the most current knowledge about the biology of Pap test abnormalities and addresses new screening technologies that have appeared in the past decade.

There are three key areas of change in the revised system: sample adequacy, terminology for atypical squamous cells that are associated with an increased risk for a premalignant lesion, and terminology for benign cellular changes.

The Bethesda System has always required the smear interpreter to evaluate the adequacy of cervical cell samples based on a standard set of criteria. The 2001 Bethesda System incorporates criteria that are specific to the new thin-layer or liquid-based cell collection method now used by many American doctors.

The older Bethesda System grouped all squamous cells considered equivocal ---that is, atypical but not clearly precancerous --- into one category known as atypical squamous cells of undetermined significance, or ASCUS. The Bethesda 2001 System adds a new category for atypical cells that have a higher risk of association with premalignant lesions: "atypical squamous cells -- cannot exclude a high-grade lesion" or "ASC-H."

By highlighting such cases, the new system should help physicians detect and treat
precancerous lesions more rapidly. In addition, the term "atypical squamous cells favor reactive" has been eliminated in order to focus greater attention on women at higher
risk of an epithelial abnormality.

The previous version of Bethesda included a category of "benign cellular changes" to communicate findings due to a variety of factors (namely, inflammation). However, this approach occasionally caused confusion for clinicians who questioned whether the term indicated negative results or the need for follow-up. Now such benign changes are more clearly identified as "negative."

In addition, The Bethesda 2001 System recommends that laboratories report use of computerized scanning of Pap test slides or use of molecular assays such
as tests for human papillomavirus.

More than 90 percent of laboratories in the United States use The Bethesda System, as do laboratories in many other countries. To date, more than 20 national and international societies have endorsed Bethesda 2001.