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Measuring diagnostic accuracy of using digital slides in routine histopathology and analyzing sources of diagnostic errors
László FÓNYAD
1st. Dept. of Pathology and Experimental Cancer Research, Semmelweis University, Budapest, Hungary, 3DHISTECH Ltd., Budapest, Hungary
Measuring diagnostic accuracydigital slides in routine histopathology
The role of
digital slides
in pathology
Our questions
RecommendationsBackground Materials & methods Results
Designing a
retrospective,
comparative
study
Statistics can be
made to prove
anything –
even the truth
What should
the FDA
regulate?
Background
• Spreading of digital microscopes (DM) Worldwide is unquestionable.
• Reports have been published concerning the reliability of digital slides (DS) in
routine diagnostics showing great advances in the technical parameters of the
scanning process and in diagnostic confidence.
• The real revolution of DSs are still waited for. Today the most common fields of
using DSs are only research, education and as a paradox: quality controll.
• We wanted to estimate the major causes of dislike and/or dissatisfaction that could
explain the mistrust in DS therefore interfere the real breakthrough of this techique in
the routine work.
Measuring diagnostic accuracydigital slides in routine histopathology
Background
Our questions were:
• Can we define a list of samples according to the origin and type of stain etc.
where the DM is sufficient to use in routine practice and define those where it
is not recommended?
• Is it possible to estimate the type of errors resulting in misdiagnosed cases?
• Does the pathologists’ interpretative skills and experience effect the diagnostic
results using DM and how important these factors are comparing to the actual
quality of the DS and working conditions?
Measuring diagnostic accuracydigital slides in routine histopathology
Materials & methods
Materials:
•Scanners and softwares were provided by the 3DHISTECH Ltd., Budapest
•280 cases were enrolled to the study
•1771 slides were scanned
•994 H&E, 70 Giemsa, 174 other special stains (mainly PAS, Prussian-blue, picrosyrius, Masson's trichrome), 553 immunohistochemistry slides. No smears or cytology samples were scanned.
•1530 were evaluated by the pathologists for digital diagnose
Table 1., Enrolled cases according to the localisation
skin 49
bone marrow 10
breast 26
upper GI-tract 37
soft tissue 21
liver 26
lymphnode 18
thyroid gland 15
lung 22
large bowel 27
kidney 29
Measuring diagnostic accuracydigital slides in routine histopathology
Materials & methods
Method:
•7 pathologists
•Pathologista A, B and D received cases, specific to their field. Pathologist C, E, F, G received non-field specific cases too.
•Initially, only those slides that were available for the first assessment (mostly HE) were uploaded to the digital database.
•A Clinical Researc Form was filled out.
•The diagnostic concordance and the reasons related DS to diagnostic uncertainity were analyzed.
•The incoherent cases were graded and 4 types of diagnostic errors were defined.
A. Scan quality
1-Unacceptable
2-Poor
3-Adequate
4-Good
5-Excellent
The reason of dissatisfaction
Important areas of the slide are out of focus (y/n)
Incomplete scan (y/n)
The color fidelity is poor (y/n)
Other (free text)
B: Diagnostic confidence
1-Uncertain
2-Likely
3-Confident
The reason of uncertainty is due to:
Case complexity (y/n)
Poor image quality (y/n)
Types of diagnostic error
Type I. non relevant incoherence – uncertainty recorded.
Type II. non relevant incoherence – uncertainty not recorded.
Type III. relevant incoherence – uncertainty recorded.
Type IV. relevant incoherence – uncertainty not recorded.
Measuring diagnostic accuracydigital slides in routine histopathology
Results
Technical results:
•Scantime ratio: 1,215 min/cm2
•Average quality of the 1530 slides was 4,45/5.
•At 34 slides the reason of dissatisfaction was that “important
areas of the slide were out of focus”. Twice the scan was
considered incomplete and 10 times the color fidelity was
rated poor.
Measuring diagnostic accuracydigital slides in routine histopathology
Results
Diagnostic results
diagnostic confidence (1-3)
uncertainty due to poore image quality
concordant
discordant reassesed incoherent non-rel - recorded
non-rel - missed
rel - recorded
relevant - missed
2,74 4,64% 78,57% 21,43% 9,64% 11,79% 1,07% 2,50% 5,71% 2,50%
Measuring diagnostic accuracydigital slides in routine histopathology
Results
Diagnostic results
Can we define a list of samples according to the origin where the DM is sufficient to use in routine
practice and define those where it is not recommended?
Measuring diagnostic accuracydigital slides in routine histopathology
Results
Diagnostic results
Does the pathologists’ interpretative skills and experience effect the diagnostic
results using DM?
Results excluding non-field specific cases:
number of cases
concordant discordant reassesed incoherent non rel - recorded
non rel - missed
rel - recorded
rel - missed
% % % % % % % %
280 78,57% 21,43% 9,64% 11,79% 1,07% 2,50% 5,71% 2,50%
172 83,14% 16,86% 8,72% 8,14% 0,58% 0,00% 5,81% 1,74%
Measuring diagnostic accuracydigital slides in routine histopathology
Recommendations
1. Based on others and our results we think that the level of diagnostic confidence using digital
slides are acceptable.
2. Reasons responsible for diagnostic errors are mostly personal and reflects the competency of
the examiner.
3. Technical reasons, potentially responsible for errors (poor color fidelity, blurred image) are
detectable by the examiner and correction of it could be initiated. (rescan, recut, restain etc.)
4. However strict regulations required for the scanning process inserted to the
prediagnostic phase
• Safety of sample recognition: how do we prevent data loss because of incomplete scan.
• Proper glass slide handling: provide accurate slide ID recognition.
• Minimalize the chance of breaking glass slides during scanning process.
Measuring diagnostic accuracydigital slides in routine histopathology
Measuring diagnostic accuracy of using digital slides in routine histopathology and analyzing sources of diagnostic errors
László FÓ[email protected]
1st. Dept. of Pathology and Experimental Cancer Research, Semmelweis University, Budapest,, Hungary
Thank You for Your attention!