The ThinPrep Imaging System (TIS) was implemented at Brooke Army Medical Center (BAMC) in February 2006 and has been a crucial part of the ability of the Department of Pathology and Laboratory Services ability to improve efficiency and turnaround times for Papanicolaou (Pap) test reporting. The increased detection rate of squamous abnormalities, specifically high-grade squamous intraepithelial lesions (HSIL), has been well documented by many studies. In addition, the TIS has increased productivity for many laboratories. The objective of this study was to evaluate the effects of implementing the TIS at BAMC, a tertiary military medical center. Specifically, the following were assessed: 1) whether the detection of squamous abnormalities was increased with the TIS, 2) how the rate of high-risk human papillomavirus (HR-HPV) detection in atypical squamous cells (ASC) of undetermined significance (ASC-US) cases changed (or did not change) before and after implementation of the TIS, and 3) how the TIS influenced productivity.
All gynecologic cytology at BAMC has been collected and processed using the ThinPrep system since 2002. Before February 2006 and before implementation of the TIS, Pap tests were screened manually by the cytotechnologists. Detection rates of squamous abnormalities were compared between the period from February 2005 to December 2005 (manual screening) and the period from February 2006 to December 2006 (image-assisted screening). Squamous abnormalities included ASC-US; ASC, cannot rule out HSIL (ASC-H); low-grade squamous intraepithelial lesion (LSIL); HSIL; glandular abnormalities; and malignancies (squamous or glandular). In addition, the rates of HR-HPV-positive, HR-HPV-negative, and HR-HPV-quantity not sufficient were compared for the same periods. During both periods, testing for HR-HPV was performed only on ASC-US Pap tests. HR-HPV was tested with Digene Hybrid Capture 2 methodology. Productivity was calculated as the change in average slides screened per hour before and after imager implementation.
In total, 107,647 Pap tests were analyzed in the 2005 (54,438 Pap tests) and 2006 (53,209 Pap tests) timeframes. Increases in the detection of ASC-H, atypical glandular cells (AGC), LSIL, and HSIL were statistically significant. The proportion of negative for intraepithelial lesion or malignancy (NILM) and unsatisfactory cases decreased significantly with implementation of the TIS. The ASC to squamous intraepithelial lesion (ASC:SIL) ratio decreased from 1.5 to 1.0 after TIS implementation. Decreases in the ASC-US HR-HPV-positive proportion and increases in the ASC-US HR-HPV-negative proportion after implementation of the TIS were statistically significant. In our laboratory, a 60% increase in productivity was noted with use of the TIS.
Implementation of the TIS at BAMC significantly increased the detection of ASC-H, AGC, LSIL, and HSIL but had no significant impact on the ASC-US detection rate. Although the ASC-US rate did not change, both the HR-HPV-positive rate and the ASC:SIL ratio decreased. The data from the current study suggested that, at least initially, the use of imager-directed screening may increase the number of clinically insignificant ASC-US Pap tests.