Original contributionWhole slide images for primary diagnostics of gastrointestinal tract pathology: a feasibility study
Introduction
Traditionally, the examination of glass slides under a microscope has been common practice for both histopathology and cytology [1], [2]. Developments in imaging technology have led to the introduction of new methods of slide examination, such as digital snapshots and live telepathology [3], [4], [5]. For more than a decade, digital slide scanners that produce digital slides, also called whole slide images (WSIs) [6], [7], have been available.
These WSIs can be examined on a computer screen by the aid of viewers that enable examination of the whole slide in a way comparable with conventional microscopy, navigating through the slide in any direction and at varying magnifications (obviously limited by the scanning magnification and the image resolution) [8], [9], [10]. Image viewers offer additional features such as an overview image to facilitate navigation within the examined slide and examination of multiple slides at the same time, allowing side-by-side comparison of different stainings of the same specimen [8], [11], [12].
Other advantages of WSIs could also be effectively used in daily pathology practice. Multiple people can open the same slide from different locations at the same time. This facilitates, for example, remote pathologic consultation and will speed up the work flow, eliminating the time needed for transferring the glass slide to remote places and improving the level of patient care [12], [13]. The use of WSIs also facilitates pathology discussion panels through Internet portals where participants can look at the slides from anywhere at any suitable moment and leave their comments [6], [12]. In addition, WSIs eliminate the risk of slide breakage, loss, and fading of stains.
WSIs have been used in many applications in daily pathology, for example, remote consultations, primary frozen section diagnosis, quality assurance, education, and research [12], [13], [14], [15], [16], [17]. However, WSIs use in daily routine diagnosis is still a matter of debate, although some laboratories have performed local (smaller) validation studies and used digital slides for primary diagnostics. The most important factor that hinders their use is the lack of systematic validation in sufficiently sized studies, and in the United States, there is no approval from the Food and Drug Administration to use WSIs for up-front diagnostics. Therefore, further validation of WSIs for up-front digital diagnostics remains necessary.
In previous articles, we have described the setup of a workflow enabling scanning and archiving of all diagnostic slides in the daily routine [6]. These scans are being used for clinicopathologic meetings, comparisons with new material, education, and research. Furthermore, we have reviewed the current status of the field of digital pathology and described our perspective on the future of digital pathology [12]. The aim of the present study was to evaluate the WSIs for up-front routine digital diagnosis in gastrointestinal pathology practice, a major field in histopathology.
Section snippets
Materials and Methods
This study was conducted in the Department of Pathology, University Medical Center Utrecht, a medium-sized academic pathology laboratory in The Netherlands handling about 144 000 surgical pathology slides per year (from about 25 000 specimens) and 12 000 cytology slides each year. Since November 2007, all histopathology slides have routinely been scanned after being diagnosed by light microscopy. Scanning is performed on ScanScope XT scanners (Aperio, Vista, CA). The whole process of scanning
Results
From the 100 cases, 95 cases (95%) were concordant, and 5 cases (5%) showed slight discordance between the digital and the light microscopy diagnoses. The percentage agreement between light microscopy and WSI diagnoses falls within the 95% CI (0.89-0.98). In addition, these 5 discrepancies were without any clinical or prognostic implications for the patient. Reassessment of the glass slides and WSIs by the reviewing pathologists showed that in 2 cases, the light microscopy diagnosis was the
Discussion
The aim of this study was to test the validity of WSIs for diagnosis of gastrointestinal tract specimens. In 100 biopsies and resections from the gastrointestinal tract, blinded rediagnosis by the same pathologist on WSIs was concordant with the light microscopy diagnosis in 95% of cases, the remaining 5% (all biopsies) being slightly discordant without clinical or prognostic implications. There were no major discrepant results, especially no discrepancies between benign, dysplasia, and
Acknowledgment
We thank Dr Roxana Ion, Philips Digital Pathology, Eindhoven, The Netherlands, for the help with statistics.
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