1. Measuring Accuracy in Digital Pathology Ole Eichhorn Chief Technology Officer, Aperio FDA panel discussion, Oct 22-23, 2009

2. Measuring Accuracy in Digital Pathology
Develop Method to Record Diagnoses
Develop Method to Compare Diagnoses ?
Develop Method to Determine Ground Truth
Record Diagnoses, Truth, Compare for Accuracy ? ? ? ?

3. Method to Record Diagnoses
Pathology reports are complex: English text with medical terms
Different reports may correspond to same diagnosis
Nuances in reports vary by lab, by region, by training, by age, etc.

4. Method to Record Diagnoses
Record diagnoses in structured way
Tissue- and preparation- specific
Use corresponding CAP* checklist for Primary Diagnosis (most prevalent or most significant finding)
Record all Significant Features
Cross-check to ensure diagnosis is recorded consistently
Can be used for all diagnoses regardless of method (conventional microscopy or digital pathology)
* College of American Pathologists

5. Method to Compare Diagnoses?
Recorded Diagnosis is a “tree” of choices
Compare two trees, assess severity of each difference
Most severe difference is overall comparison result:
ND = no difference, I = incidental, S = significant,
CS = clinically significant (affects patient care)
ND, I, S, CS

6. Method to Determine Ground Truth
Nature of Pathology
Pathology is inherently subjective
Many cases are “obvious” (most pathologists agree)
Difficult cases are typically diagnosed via consultation
Record Ground Truth in structured way
Convene panel of expert pathologists
Diagnose using conventional microscopy
Resolve disagreements using consultation
Record consensus using Method to Record Diagnoses

7. Process to Measure Accuracy
Record Diagnoses
Determine Ground Truth
Compare Diagnoses to Ground Truth ? ? ? ?
Measure Accuracy