Further Rejection of Null Hypothesis: Digital Pathology Equal to Glass Slides

| December 21, 2015
Since the inception of commercially available whole slide imaging systems more than 15 years ago, a necessary requirement has been to prove that diagnoses made using DP alone are equal to or better than conventional glass slides (GS) that have been used for at 10 times longer to care for patients.
That is to say, the null hypothesis has been that whole slide imaging is inferior to the light microscope and in turn, the reproducibility, accuracy and consistency of pathologists to reliably make the “gold standard” diagnosis using DP was inferior to GS.
Many investigators since the early 2000s have sought to reject this null hypothesis through the scientific method with now 100s of papers published detailing thousands of cases to validate the technology for primary opinion, demonstrating equivalency and in some cases, superiority of DP compared with GS diagnoses.
nhsNow comes additional study from Dr. David Snead and colleagues at University Hospitals of Coventry and Warwickshire NHS Trust in the UK who examined 10,138 scanned slides and found 72 variances between GS and DP, including 21 clinically significant variances where the ground truth lay with GS in 12 cases and with DP in 9 cases. Seventeen pathologists reported 3,017 cases by DP. Of these 1,009 were reported by the same pathologist and 2,008 by a different pathologist (than the original GS interpretation). Their findings entitled, Validation of digital pathology imaging for primary histopathological diagnosis, using Omnyx, were reported in Histopathology in September.
The authors concluded “This is one of the largest studies proving DP is equivalent to GS for the diagnosis of histopathology specimens. Error rates are similar in both platforms, although some problems e.g. detection of bacteria are predictable.”
The authors also report there are inherent variabilities in pathologists’ diagnoses that are well known, including intra- and inter observer differences that make studies of these kinds require some recognition of establishing “ground truth” and potentially limited reproducibility using a single modality.
This is clearly encouraging news for the digital pathology community towards showing equivalency among DP and GS diagnoses between and amongst pathologists.
I think it also shows that with current technologies, there are going to be a subset of cases, with increasing accuracy towards predicting which ones, where DP may actually be superior to the light microscope or where light microscope techniques (rare organism detection or polarized light examination) may still be required.
DOTmed.com ran a nice article by Lisa Chamoff that details the implications for their HealthCareBusiness section

Researchers in the UK have determined that whole slide imaging is just as effective for making a primary cancer diagnosis as examining glass slides under a microscope, with the future potential for digital systems to use algorithms to help separate normal from abnormal samples and grade cancers.

The study, one of the largest and most comprehensive validation studies of whole slide imaging for clinical use, was published earlier this month in the journal Histopathology.

omnyx.logo.refresh_100824The 17 pathologists at University Hospital Coventry used a computer system called The Omnyx Precision Solution, which digitizes slides that are traditionally placed under a microscope and allows pathologists to look at them on a computer. They evaluated biopsies and resections from more than 3,000 patients using both microscopes and the digital pathology system, determining if there were any statistical differences in the accuracy of the diagnoses.

Out of 3,017 cases, there were 72, or only 2 percent, where the glass slide and digital case diagnosis did not agree with each other. In just three cases, the digital platform was determined to be responsible for the variance, including a bronchial biopsy and penile biopsy, where dysplasia was reported on digital pathology but was not present on glass slide microscopy.

The results are within the 95 percent confidence interval for existing variability, proving that digital pathology is non-inferior to glass slide microscopy, the researchers concluded.

David Snead, a pathology consultant at University Hospital Coventry and an author of the study, explained that while the Omnyx system is not approved for primary diagnosis by the U.S. Food and Drug Administration, and can only be used for secondary diagnosis in the U.S., it’s up to individual institutions in the UK to determine whether the technology satisfies the requirements for putting it into practice.

“We’re confident that it works pretty well,” Snead told HCB News. “This study showed that you can use this technology for primary diagnosis.”

Snead said the FDA will likely look at his group’s study when making a decision about approving digital pathology for primary diagnosis in the U.S.

Read more about the research findings and remarks from Omnyx’s CEO.




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