Effectiveness of the ThinPrep Imaging System: clinical experience in a low risk screening population

The Cytyc ThinPrep Imaging System was FDA approved based on a multi-institutional clinical trial, in which the HSIL+ prevalence rate was 0.7%. This study determines the effectiveness of the Imager in clinical practice at an academic medical center with a historical HSIL+ rate of 0.25%. Cytological interpretations were compared for two 12-month periods pre- and post-Imager implementation. Data was compiled by cytologic diagnoses, and variations in prevalence rates were analyzed for statistical significance. Interpretations of ASC-US, ASC-H, and LSIL were correlated with Digene Hybrid Capture2 High Risk HPV DNA testing; interpretations of ASC-H, LSIL, and HSIL+ were correlated with subsequent surgical follow-up. ASC-US, ASC-H, and LSIL detection rates increased 34, 48, and 29%, respectively, with the Imager (P<0.001); whereas the detection of HSIL increased 24% (P<0.051). Surgical correlation revealed no statistical differences in the positive predictive value (PPV) for ASC-H and LSIL. However, an increase in the PPV of HSIL was found (P<0.05). High risk HPV results were lower for ASC-US (P<0.001), but statistically equivalent for ASC-H and LSIL. Results of surgical correlation and HPV testing validated an increase in detection rates of ASC-H, LSIL, and HSIL, as well as increased PPV of HSIL with the ThinPrep Imaging System.