Page 16 - Screening for Cervical Cancer: Systematic Evidence Review

Chapter I. Introduction

abnormalities may be identified by screening but not properly treated as a result of patient or

provider failure to follow-up the abnormalities; this may occur in approximately 22% to 63% of

those who receive proper screening. Second, serious abnormalities may not be present at the

time of screening, and progression occurs between recommended screening intervals. When the

interval is annual, such progression is rare; with 3-year intervals, this may happen in up to 50%

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of diagnosed cases. Progression is more common among women under 45 years of age. Third,

abnormalities may be present but are not detected by the screening test (approximately 14% to

33%). 24,25 The last category of failures, those related to the screening test, can be further

subdivided into those that represent sampling error (cells from the abnormal area were not

obtained and so could not be identified in the specimen) and those that reflect detection error (the

abnormal cells are included in the specimen and are not identified as abnormal).

Screening Tools

This report is focused on cervical cancer screening tools for clinical use in primary care

settings. We consider traditional cytology and new cytologic technologies that are currently

available to practitioners. HPV testing to identify specific types of HPV is less broadly

available. Some HPV test methodologies such as Southern blot are appropriate as a gold-

standard assay but not practical for widespread implementation in a cervical cancer screening

program. As a result, we have focused on HPV tests suitable for high-volume use as part of

primary clinical care. Basic descriptions of available cytologic and HPV screening tools are

provided below.

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