Does the ThinPrep Imaging System increase the detection of high-risk HPV-positive ASC-US and AGUS? The Women and Infants Hospital experience with over 200,000 cervical cytology cases

Background: Published reports have demonstrated that introduction of the ThinPrep Imaging System (Imager) to the cytology screening services has increased the detection rate of high-grade squamous intraepithelial lesions (HSILs). In accordance with recent clinical treatment guidelines, patients with atypical squamous or glandular cells of undetermined significance (ASC-US or AGUS) are often tested for high-risk HPV infection using the Hybrid Capture HPV DNA test. We took the opportunity to investigate whether the Imager had resulted in any significant differences in our diagnostic categories, as well as whether the Imager increased the detection of high-risk HPV-DNA-positive (HRHPV+) ASC-US or AGUS.

Materials and methods: Cytology cases with the diagnosis of ASC-US and AGUS were retrieved from the archival files of our institution during periods of 11 months prior to and 11 months after the introduction of the Imager. The total number of cases in each category was correlated with results of reflex high-risk HPV DNA testing when the latter were available. All AGUS diagnoses were correlated with subsequent biopsy follow-up. Statistical analyses were performed using the chi-Square test with Yate's Correction and Fisher's Exact test.

Results: A total of 108,371 and 104,555 of ThinPrep Pap Test (TPPT) cases were reviewed during 11 months pre- and post-imager introduction. The ASC-US rate was 5.4% in the pre-Imager and 5.3% in the post-Imager period. The HPV reflex test was 38% and 34% positive respectively in the pre- and post-Imager period (P>0.124). Similarly, 0.14% and 0.12% AGUS were found in the pre- and post-Imager period. The positive HPV reflex test was 14% versus 23% (P = 0.1690). The abnormal biopsy follow-up rate in the AGUS category was increased from 20.9% in the pre-Imager period to 31% in the post-Imager period (P = 0.1471). The ASCUS/SIL ratios were 1.9 and 1.6 respectively.

Conclusions: The ASC-US and AGUS rates did not change statistically before and after the introduction of the Imager in our cytology laboratory. Although use of the Imager did not increase detection of HPV+ ASC-US, it did appear to increase the detection rate of HPV+ AGUS and subsequent abnormal biopsy follow-up rates in all categories. However, the increase in the detection rate did not reach the point of statistical significance.