Homogeneous Sampling Accounts for the Increased Diagnostic Accuracy Using the ThinPrep^™Processor

Abstract

Recent clinical trials indicated that the ThinPrep method of sample preparation has greater diagnostic sensitivity than the conventional direct Papanicolaou smear. The authors hypothesized that nonhomogeneous cell sampling during transfer from the sampling device to the microscope slide was a contributing factor to the reduced accuracy of the conventional direct Pap smears in these trials. To test this hypothesis, four direct smear methods were compared with the newly developed, fluid-based, filter-transfer method. Counts of epithelial cells on conventional smears showed that only a fraction of the available epithelial cells on the sampling devices (medians, 6.5% to 62.5%) was actually deposited on the slides. In all 27 cases studied with the ThinPrep method, equivalent diagnostic material was obtained on each of the replicate slides prepared per specimen. This identifies a new source of error, preparation error, in conventional smears.

Direct comparison of liquid‐based and conventional cytology in a South African screening trial

“…A commonly cited advantage of LBC is that, unlike conventional smears, for which only a selective portion of cellular material is transferred to the slide, almost all sampled cells are rinsed into the liquid and dispersed throughout. 28 As a result, LBC is thought to produce smears that are more representative of the entire sample, thereby, facilitating the detection of abnormal cells when only a few such cells have been adequately sampled.…”

Comparative Analysis of Conventional and Thin Prep Papanicolaou Test. Technical and Economic Aspects

“…According to Hutchinson et al [32], more than 80% of collected cells from the cervix are not deposited in the glass slides. Moreover, it is not possible for gynecologists to select a representative sample for the slide.…”

Interobserver variability

“…15 The enhanced detection of epithelial cell abnormalities by TP is due in part to improved sampling and a lack of obscuring blood, inflammation, and mucus. 26 There are only a few studies addressing interob- server variability in diagnosing gynecologic cytology using TP. In a recent study, 3 pathologists and 1 senior cytotechnologist reviewed 144 TP slides previously diagnosed as WNL, ASCUS, and SIL.…”

“…For example, the epithelial cells in the conventional cervical smears often were distributed unevenly over the slide and aggregated in overlapping groups, whereas the TP cervical slides displayed cells that were distributed more evenly within a 22-mm circle and with minimal overlap. 26,27 Better cell preservation and visualization due to lack of air-drying artifacts and obscuring inflammation and blood also contributed to the improved quality of TP. 14,15,27 A recent study reported an increase in the rate of completely satisfactory specimens from 80% to 90% and a decrease in the rate of satisfactory but limited by… findings by 46% with the use of TP.…”