Whole slide images for primary diagnostics of gastrointestinal tract pathology: a feasibility study

Summary

During the last decade, whole slide images have been used in many areas of pathology such as teaching, research, digital archiving, teleconsultation, and quality assurance testing. However, whole slide images have as yet not much been used for up-front diagnostics because of the lack of validation studies. The aim of this study was, therefore, to test the feasibility of whole slide images for diagnosis of gastrointestinal tract specimens, one of the largest areas of diagnostic pathology. One hundred gastrointestinal tract biopsies and resections that had been diagnosed using light microscopy 1 year before were rediagnosed on whole slide images scanned at ×20 magnification by 5 pathologists (all reassessing their own cases), having the original clinical information available but blinded to their original light microscopy diagnoses. The original light microscopy and whole slide image–based diagnoses were compared and classified as concordant, slightly discordant (without clinical consequences), and discordant. The diagnoses based on light microscopy and the whole slide image–based rediagnoses were concordant in 95% of the cases. Light microscopy and whole slide image diagnosis in the remaining 5% of cases were slightly discordant, none of these were with clinical or prognostic implications. Up-front histopathologic diagnosis of gastrointestinal biopsies and resections can be done on whole slide images.

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.