4. Hrvatski kongres kliniËke citologije 4th Croatian Congress ... - Penta

4. Hrvatski kongres kliniËke citologije / 1. Hrvatski simpozij analitiËke citologije / 2. Hrvatski simpozij citotehnologije
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Klinička citologija - Plenarna i pozvana predavanja
BENEFITS OF LIQUID BASED CYTOLOGY OVER CONVENTIONAL PAP TEST:
PRESENT AND FUTURE.
Verhest A
Institute Jules Bordet, Brussels - Belgium
Objective:The intention of this presentation is to provide insight into our everyday experience
with the BD-SurePath TM liquid based technology that we used for cervical cancer
screening since 1998. We will also focus on use of reflex HPV-DNA testing as an adjunct
for external quality control and guided screening of cervical cytology specimens as a
significant advance over routine manual screening . Methods:Conventional Pap screening
has been credited with a 75 % reduction in cancer incidence and death rates in the
last 50 years. Despite this, there was a growing evidence of a limited sensitivity of 77 %
for detecting CIN 2 (when using LSIL as a threshold) with an individual Pap smear, a low
positive predictive value (10-30%), a highly subjective interpretation leading to misclassification
with unreducible false negative and positive rates. These factors limiting the
performance of the Pap smear while increasing the complexity and costs of screening
programmes, we replaced conventional smear in december 1997 by thin layer preparations
made with BD-PrepStain TM automate from samples collected in BD-SurePath
TM preservative fluid. Liquid based cytology (LBC) diagnoses were assessed on first
screening sample with a second reading combined with HPV test to improve the ASCUS
predictive value and offer an immediate evaluation of our personal performance and
possible misinterpretation of the Bethesda TBS criteria. The LBC process is now widely
used in the United States, many European countries and elsewhere. The slides facilitated
the screening by skilled human observers or triggered an impetus for automated
screening. In order to determine if use of the BD FocalPoint GS Imaging System (BD
Diagnostics-TriPath) is more effective than manual screening, a large clinical trial has
been recently performed. (1) A 2-armed, masked trial was run at 4 clinical sites. 12,313
slides were evaluated. The control arm (CA) consisted of routine manual screening and
quality control (QC) rescreening. The experimental arm (EA) consisted of screening by
the BD FocalPoint GS Imaging System. Results: With the adoption of LBC we have
significantly reduced the number of unsatisfactory smears minimizing cellular preparation
artifacts, decreased the ASCUS rate and improved the sensitivity and specificity
of our SIL diagnoses. The use of HPV testing has ascertained our diagnoses in the
necessary learning curve of our morphologic interpretation of abnormals. BD-SurePath
TM increased comfort and skill level of the all staff. More evenly dispersed single-cell
population between aggregates enhances the clarity of the smear, makes them easier
to evaluate for atypia; its utilization demonstrated evident superiority over conventional
Pap smear in terms of disease detection. Using computer-assisted imaging, all positive,
discordant, and a subsampling of negative slides were adjudicated to a reference
diagnosis. The results obtained in the two arms were compared to the reference diagnoses
and sensitivity, specificity, and negative predictive value (NPV) were calculated
for ASC-US+, LSIL+ and HSIL+ groups. (1). The FocalPoint LGS reading gives a higher
detection sensitivity than the manual reading for HSIL+ and for LSIL+. (1-2) For ASC-US+,