Comparison of the sensitivity of conventional cytology and the ThinPrep Imaging System for 1,083 biopsy confirmed high‐grade squamous lesions

Abstract

Liquid-based cytology continues to be utilized as an adjunct to conventional cytology in most Australian laboratories, even though a direct-to-vial ThinPrep protocol has been introduced in many countries with established cervical screening programs. Manual screening of ThinPrep slides has been widely practiced for more than 10 years and the recent introduction of the ThinPrep Imaging System (TPI) has been reported as being more sensitive than the conventional smear (CS) in the identification of high-grade cervical disease.We report our experience with ThinPrep Imaging since its introduction into our routine gynecological cytology service. 87,284 split sample pairs reported using the Imaging System demonstrated a decrease in unsatisfactory reports (3.65% for CS and 0.87% for TPI) and an increase in possible high grade and definite high-grade squamous reports (1.57% for CS and 1.62% for TPI).For 1,083 biopsy confirmed high-grade lesions, the correct diagnosis of high grade or possible high-grade squamous disease was made on the ThinPrep imaged slide in 61.0% (661/1,083) of cases and on the CS in 59.4% (643/1,083). This was not statistically significant. When all abnormalities identified on cytology were considered, including possible low grade and definite low-grade abnormalities, the difference in sensitivity for Thinprep imaged slides of 96.0% (1,040/1,083) and CSs of 91.6% (992/1,083) was statistically significant.

MAVARIC – a comparison of automation-assisted and manual cervical screening: a randomised controlled trial

“…There are reasons why automated reading could result in false-negative reports. Peripheral location of abnormal cells in the FOVs was found in a number of cases, also noted by Halford et al's 16 study. This is not a problem in manual screening given the practice of overlapping fields in routine screening practice, which is lost in location-guided screening.…”

“…the abnormalities had not been shown on the FOVs. In a similar review by Halford et al, 16 discordant readings from a split sample study, 31/37 cases of auto misses were found to contain abnormalities on the FOVs not detected in the initial read, and in the majority of these 31 cases abnormal cells were seen in only 5 out of 22 FOVs. There are reasons why automated reading could result in false-negative reports.…”

“…6 As stated in Chapter 1 and shown in Table 1, previous studies comparing automated with manual reading have tended to indicate higher rates of cytological abnormality and some have found increased rates of CIN2+. Some of these studies 23,27 have been performed simply comparing cytological abnormality rates in consecutive periods of time, and others have used a split sample design, 16,24,26 whereby the same sample has been split between a conventional or LBC slide which is manually read and a slide which is subjected to automated reading. Many studies do not use histology as an outcome.…”

“…Discrepancies between the Abbott and Digene assays' results were resolved using the Roche LINEAR ARRAY genotyping test, which detects 37 anogenital HPV types, 6,11,16,18,26 …”

“…This involves an in vitro nucleic acid hybridisation assay with signal amplification using microplate chemiluminescence for the qualitative detection of HPV types 16,18,31,33,35,39,45,51,52,56,58,59 and 68 in cervical specimens.…”