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Liquid Based Cytology.pptx
1. LIQUID BASED CYTOLOGY
BY
DR. A. B. AJILEYE
DEPARTMENT OF BIOMEDICAL LABORATORY SCIENCE,
COLLEGE OF MEDICINE, UNIVERSITY OF IBADAN.
2. Introduction
• Liquid based cytology is a technique that enables cells to be
suspended in a monolayer and thus making better morphological
assessment possible with improved sensitivity and specificity.
• The sample is collected, normally by a small brush, in the same way
as for a conventional smear test, but rather than the smear being
transferred directly to a microscope slide, the sample is deposited
into a small bottle of preservative liquid. At the laboratory the liquid
is treated to remove other elements such as mucus before a layer of
cells is placed on a slide. The technique allows more accurate
results.
• To provide uniformity of the cell population in each sample.
3. • From recent research and development, liquid-based
preparations out perform conventional smears because of
improved fixation, decreased obscuring factors, and
standardization of cell transfer.
• In direct smears, the cells are not transferred in a
representative fashion and that up to 90% of the material
scraped from the cervix may be discarded with the
sampling device.
10. Microscopically, the uneven
distribution of cellular material
associated with the Conventional
Pap Smear pattern is evident.
This slide is from the same patient as the
Slide by the left hand side. Tissue architecture is
maintained. ThinPrep® rearranges the
relationship of cell groups on the glass slide. A
group/sheet of endocervical cells present
represents this.
11. • Reasons for Unsatisfactory Smear (Conventional Pap
smear)
The following inhibits interpretation of 75 % of smear : -
• Squamous epithelial component scanty/absent
• Obscuring blood
• Inflammation
• Thick areas
• Mucus
• Poor Fixation
• Air Drying
• Artifact
• Contamination
12. Disadvantages of Conventional PAP smears:
• Despite the demonstrated ability
of cervical cytological screening to reduce cervical cancer, inc
idence and mortality, the conventional Pap test is less sensitive
than is generally believed. The false negative rate of the
conventional Pap test has been reported to be up to 50%.
• Approximately 67% of false negative results are attributable to
improper sampling techniques or the poor quality of slides. Sa
mpling errors may
result when a slide does not contain a representative sample of
the cells from the cervix, or the
cells are obscured by mucous or blood, or are inadequately prese
rved.
• Common findings on conventional Pap smears include: -
thicker and thinner smeared areas, air drying artifact-
variety of artifacts, such as “nuclear feathering
13. Principles of the preparation of Liquid Based
Cytology (LBC) slides
• A sample of cells is collected from the cervix in the same
manner as is used in the conventional Pap test, using either
a broom type device or a plastic spatula or a cytobrush.
• Rather than smearing the cytological sample directly onto a
microscope slide, the sample cells are transferred into a
container of preservative/transport medium.
• The cell are dispersed in the fluid
• An aliquot of the suspension is selected for processing
• The cells are separated by centrifugation or filtration and
deposited on a slide as a thin layer/monolayer by
sedimentation or the application of pressure
• The slides are stained, mounted and ready for microscopy
17. Thin Prep Method
• The heart of the ThinPrep® System is the ThinPrep 2000
Processor, a semi automated slide preparation unit that
produces remarkably uniform thin-layer slides, virtually
free of obscuring artifacts such as blood, mucous and
inflammation.
• Step 1
• A gynecologic sample is collected using a broom-type or
cytobrush/spatula cervical sampling device.
18.
19. Step 4
At the laboratory, the vial is placed into the ThinPrep 2000
Processor. First, a gentle dispersion step breaks up blood,
mucous, non-diagnostic debris, and then thoroughly mixes
the sample.
A negative pressure pulse is generated which draws fluid
though a TransCyt® Filter(a micropore filter) that collects a
thin, even layer of diagnostic cellular material. The
ThinPrep 2000 Processor constantly monitors the rate of
flow through the TransCyt Filter during the collection
process to prevent the cellular presentation from being too
scant or too dense.
The filter is then removed and dabbed onto an electrically
charged slide causing cells to transfer onto the glass slide.
This is then stained in a separate process using same
staining machine as is used for conventional samples.
27. • Method and principle
• The Autocyte Prep system/ Sure path method converts
liquid suspension of cervical cell sample into a
discretely stained homogenous thin layer of cells while
maintaining diagnostic cell clusters. The process
includes
1) cell preservation (preservative fluid is dil. Soln. of
denatured ethanol)
2) randomization
3) enrichment of diagnostic material
4) automated pipetting
5) sedimentation
6) staining
28. • After collection and preservation, the sample is mixed
by vortexing ( to re-suspend cells) and dispersed onto
a density reagent (contains sodium azide).
• An enrichment step consisting of centrifugal
sedimentation through density reagent partially
removes non diagnostic debris and excess
inflammatory cells from sample.
• After centrifugation, the tube containing the enriched
cellular component is placed onto the instrument
where the pelleted cells are robotically suspended,
mixed and transferred to settling chamber.
• Here a specialized slide coat is applied to enhance cell
adhesion.
• Cells are sedimented by gravity and then stained using
modified papanicolaou staining process.
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30.
31.
32. Advantages of LBC
• Immediate fixation with enhanced nuclear and cytoplasmic
detail
• All material collected is available for microscopic evaluation
• A representative sample is prepared for cytological evaluation
but multiple samples can be prepared as necessary
• Clearer background so that epithelial cells of interest are less
likely to be obscured
• A thin layer of dispersed cells are spread over a fixed area so
that the area to be screened is small and the preparation
takes less time to screen than a conventional smear
• Unsatisfactory rate decreased
• LBC samples is suitable for other tests e.g. HPV testing
• LBC slides are suitable for automated analysis
33. Disadvantages of LBC
• Smear patterns altered because of randomization of cells
• Abnormal cells are dispersed
• Scanty LBC preparations can be difficult to screen and
interpret
• Blood mucous inflammation and malignant diathesis are
still present but appear slightly different
• Epithelial cells appear mostly as single cells and are slightly
smaller than they appear in conventional smears especially
endocervical cells and immature metaplastic cells.
• LBC is more expensive than conventional test
34. Other uses of LBC
LBC ThinPrep system has found broad acceptance in non-gynecologic
cytopreparation such as:
• Thyroid cyst fluid examination.
• Oral pathology: diagnostic for various types of oral lesions.
• body fluids (e.g. urine, pleural effusions),
• brushing samples (e.g. gastrointestinal tract, lung)
• fine needle aspiration.
