VOL. 1 JANUARY 2007
Pap Test Imaging Provides Value to Both Patients and the Lab |
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Early detection is crucial in preventing and treating cervical cancer. There are no noticeable early-warning symptoms or physical changes, yet when it is detected early, it is one of the most treatable and curable of all cancers. As a result, the accuracy of cervical screening is crucially important.1 In the last 10 years liquid-based Pap testing has largely replaced the Pap smear, because of the improved specimen quality and improved sensitivity. However, after the test vial leaves the physician's office, optimizing the screening process in the laboratory is key in assuring screening accuracy.
Efforts to automate cervical screening began shortly after widespread introduction of the Pap smear in the 1950's. This proved challenging due to the unique human skills required to accurately interpret the Pap smear. It was not until the late 1990s that the first computer imager for Pap smears was approved by the Food and Drug Administration (FDA) for quality-control procedures; however, it was met with little commercial success, most likely due to a lack of clinical data demonstrating a significant increase in disease detection, exclusion of high risk patients, and suspicion towards computer-only slide review. In 2003, the FDA approved the first fully integrated, interactive computer imaging system that assists cytotechnologists in the primary screening of ThinPrep® slides. The FDA approved labeling claims include increased sensitivity and specificity (based on a statistically significant improvement in sensitivity for ASC-US+ and specificity for HSIL+).4 A key attribute of the ThinPrep Imaging System is "Dual Review™" technology which ensures every slide is analyzed by the Imager and also screened by a cytotechnologist. Cells of interest are highlighted for cytotechnologists' review, helping them to better focus interpretative skills. Independent publications have confirmed and extended the results of the FDA trials. Lozano et al. state that "Increases in the detection of LSIL and HSIL lesions are not only statistically significant but are also clinically significant", while Dziura et al. note that "Biopsy results confirmed a significant increase in the detection of HSIL."2,3 In addition, this technology has demonstrated a 39% reduction in false negative fraction over manual screening based on a statistically significant improvement in sensitivity for ASC-US+.4 Emerging data continue to substantiate claims of increased disease detection and reduced occurrence of false negative screening with the ThinPrep Imaging System with Dual Review™ vs manually screened ThinPrep slides.5 As summarized by Dziura et al., "The merger of mind and computer ... has created a better Pap test."2 In addition, in contrast to the previous imaging systems, the ThinPrep Imaging System is FDA approved for use with high-risk patients. Cervical cancer has been described by the FDA as a "silent cancer." While many cancers cause pain, detectable lumps, or other early symptoms, cervical cancer has no associated symptoms until it is so advanced that it is usually unresponsive to treatment.1 As a result, accurate cervical screening remains key in the early detection and prevention of cervical cancer. The introduction of computer imaging-assisted screening appears to hold great promise in increasing our ability to reduce false negatives compared to manual screening, and this represents an important advance in cervical screening technology. References:
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