Wednesday, September 17, 2008

The Bethesda System

By the late 1980s, advances in our understanding of the role of human papillomavirus (HPV) in the pathogenesis of cervical cancer needed to be incorporated into cytological terminology. Moreover, it was recognized that clinicians were often confused by the non standard terminologies used to report cytological results and that this had a potential adverse impact on clinical care. Therefore, in 1988, the US National Institutes of Health held a conference in Bethesda, Maryland, to develop a new terminology that would ensure better standardization and accommodate current concepts of the pathogenesis of cervical disease, so that cytological findings could be transmitted to clinicians as accurately and concisely as possible.

The terminology that resulted is known as the Bethesda System. In 1991 the Bethesda System was slightly modified on the basis of experience obtained during the first three years of its use and it was further modified in 2001 to take into account the results of new research and over a decade of experience with the terminology (Luff, 1992; Solomon et al., 2002). The Bethesda system is viewed with caution in the United Kingdom, which retains its own British Society for Clinical Cytology (BSCC) ‘dyskaryosis’ terminology (British Society for Clinical Cytology, 1997). This can largely be mapped to the Bethesda system for comparison of data in a research setting, except for the borderline category, which may include koilocytes.

Due largely to the robust nature of the ‘severe dyskaryosis’ category, fear of increasing the overtreatment inherent in cervical screening and the difficulty of achieving inter- and intra-observer agreement on ‘low-grade’ reports, the United Kingdom continues to use this terminology. There are three distinct parts to each Bethesda System report: a statement of the specimen adequacy, a general categorization and a descriptive diagnosis. These categories assist clinicians by providing answers to three basic questions:

(1) Do I need to repeat the cervical cytology?

(2) Was the cervical cytology normal?

(3) If the specimen was not completely normal, what specifically was wrong?

Because cervical cytology is considered a screening, rather than diagnostic, test, the 2001 Bethesda System reports cytological findings as an ‘interpretation’ or ‘result’ rather than as a ‘diagnosis’. This stresses the fact that cytological findings usually need to be interpreted in the light of clinical findings, and that the test is designed to reflect the underlying disease state but does not always do so.

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