Post on 26-Mar-2015
LBC – Sink or Swim?
Thames Valley Cytology Society
Bedford
24th June 2004
NICE Guidance
October 2003:
NICE recommends that LBC is used as
the primary means of processing samples
in the cervical screening programme in
England and Wales
NICE Guidance
There is currently insufficient evidence to
recommend one LBC product over
another.
The NHSCSP and SCW may wish to
consider evaluating further different
products as the method is introduced.
Conventional Smears
False Negative Rate of up to 55% Sampling and interpretative errors
Borderline Rates of up to 6.4%70% are truly negative
30% represent more severe abnormality
Inadequate Rates of 9.7%
Sources Of False NegativesSampling issues (70%)
– cells not collected on the sampling device– cells collected, but not transferred to the slide
Interpretative issues (30%)
– abnormal cells present on slide but either not seen or misinterpreted
The ProblemThe ProblemThe Problem
The Conventional Cervical SmearThe Conventional Cervical Smear
A cervical sample containing precancerous
cells (red)
A cervical sample containing precancerous
cells (red)
Non-randomized portion of cells
Non-randomized portion of cells
Over 80% of cells discardedOver 80% of
cells discarded
Smear spray-fixed and sent to lab
Smear spray-fixed and sent to lab
Missing cells, obscuring elements
Missing cells, obscuring elements
Sample may not reflect patient’s actual condition
Sample may not reflect patient’s actual condition
The Solution
The SolutionThe SolutionThe ThinPrep® Pap Test™The ThinPrep® Pap Test™
A cervical sample containing precancerous
cells (red)
A cervical sample containing precancerous
cells (red)
Virtually 100% of cells collected into
ThinPrep vial
Virtually 100% of cells collected into
ThinPrep vial
Cells immediatelypreserved and
sent to lab
Cells immediatelypreserved and
sent to lab
Filtration process disperses, randomizes cells
Filtration process disperses, randomizes cells
More representative and clear thin layer
of cells
More representative and clear thin layer
of cells
Increasedopportunity to
detect early signsof abnormality
Increasedopportunity to
detect early signsof abnormality
Evidence BaseClinical Validation ThinPrep® Improvement
Patients LSIL+ HSIL+ S.Q.Split-Sample Lee et al. 6,747 65% 36% 54%
Corkill et al. 1,583 110% 54% N/ARoberts et al. 81,754 26% 15% 91%
Direct-to-Vial Scottish Pilot 30,228 92% 84% 76%Diaz-Rosario 56,339 72% 103% ???Papillo et al. 8,574 52% 55% 52%Weintraub et al. 18,247 184% 94% 93%Bolick 10,694 181% 173% 70%Johnson et al. 902 71% 125% 41%Guidos/Selvaggi 9,583 267% 233% 97%Quddus 14,216 24% 35% 28%Hornish 30,431 N/A 83% N/A
>60 peer reviewed international publications from 4 Continents
Does LBC increase sensitivity?
Educational biasLab / Smear takers
Study design biasSplit sample / Direct-to-Vial
Population biasSelf-selecting / Non-screening
End point biasDyskaryosis as ‘surrogate’ / lack of histological confirmation
Does LBC decrease inadequate rates?
SurePath 5000 cells
Thinprep 40000 cells
Conventional 50000 cells?
Weighted Average (total 30,228)
Conventional % ThinPrep %
Unsatisfactory 7.63 1.84
Borderline 3.98 3.67Mild 1.10 2.12 92%↑
Moderate 0.45 0.97Severe 0.65 1.06 84% ↑
Scottish Pilot Results
• No major storage problems • Reduced workload for smear takers• 349/350 smear takers preferred ThinPrep®
• Increased productivity in laboratories• Sharp reduction in the unsatisfactory rate • Less anxiety and discomfort for women• More appropriate referrals to colposcopy• Allows scope for further developments in the screening programme
Scottish Pilot Conclusions
Vial storage Modular storage units available
(File-a-Vial)
150 vial capacity
Example:
• 30,000 samples pa • 4 week cycle• 2,500 vials • 17 units
ThinPrep® T2000 Processor
SurePath
Why I like the SurePath Liquid-Based
PAP Test
David R Bolick
RPS Sandy, Utah
SurePath
SurePath and ThinPrep
Similarities:
Diagnostic rates
Detection rates of HPV from vial
Histology/Cytology correlation rates
SurePath
SurePath and ThinPrep
Differences:
Inadequate rates
False negative fraction
Detection of abnormalities in clusters
SurePath
SurePath and ThinPrep
Inadequate rates:
SurePath 0.18% 26/14419
ThinPrep 0.37% 123/33198
SurePath
SurePath and ThinPrep
False negative fraction:
LSIL % HSIL %
SurePath 6.8 0.0
ThinPrep 14.0 16.0
SurePath screened TWICE ; ThinPrep screened ONCE
SurePath
SurePath and ThinPrep
Abnormalities in clusters:
AGUS Endom Adenoca
SurePath 0.13 0.24 0.05
ThinPrep 0.09 0.13 0.02
LBCLBC is on the way.
5 year conversion timescale is too long
Major retraining exercise for labs
Benefits in terms of productivity and scope for future developments
Good for smear takers and women
Issues around sensitivity / specificity / inadequate rates will be answered in long run
Expensive solution