A bridge from the view: Switching from glass to digital dermatopathology
Nov. 23, 2016
Eight months ago, I started using the Clearpath digital dermatopathology system developed by Tom Olsen and his associates at the Dermatopathology Laboratory Central States (DLCS). As one of the early utilizers, I was grateful to work with his software wizards, offering my perspectives on how to optimize the digital experience. It was with great interest that I read the article by Shah et al (1), examining the validity of whole slide imaging (WSI).
The authors conducted a retrospective WSI validation study of routine dermatopathology cases, adhering to CAP (College of American Pathologists) guidelines. A total of 181 consecutive cases arranged into 3 categories (inflammatory, melanocytic, nonmelanocytic proliferations) were reviewed by 3 board-certified dermatopathologists via traditional microscopy (TM) and WSI. Intraobserver (TM vs WSI), TM intraobserver and interobserver (TM vs TM), and WSI interobserver (WSI vs WSI) concordance was interpreted using a 3-tier system. TM versus WSI intraobserver concordance (86.9%; 95% confidence interval [CI] 83.7-89.6) did not differ from TM versus TM intraobserver concordance (90.3%; 95% CI 86.7-93.1) or interobserver concordance (WSI: 89.9%; 95% CI 87.0-92.2, and TM: 89.5%; 95% CI 86.5-91.9). Melanocytic proliferations had the lowest TM versus WSI intraobserver concordance (75.6%; 95% CI 68.5-81.5), whereas inflammatory lesions had the highest TM versus WSI intraobserver concordance (96.1%; 95% CI 91.8-98.3). Nonmelanocytic proliferations had an intraobserver concordance of 89.1% (95% CI 83.4-93.0). The authors concluded that intraobserver and interobserver diagnostic concordance between WSI and TM was equivalent. Therefore, WSI appears to be a reliable diagnostic modality for dermatopathology.
The process works as follows: We send our specimens to DLCS — they process slides in the usual manner but also digitalize the slides, making them available for review electronically. If tissue is sent on Monday by overnight mail, I will be able to see the image on Wednesday. The program is iPad-based, and handling the digital slide is almost magical. You touch the screen to zoom in and out and rotate the specimen in any direction you wish. Breslow measurements are performed by placing a finger on the granular layer followed by bringing the arrow to the depths of the melanoma for an instant, accurate reading. Requests for special stains, deeper sections, etc. are effortless. I also generate my reports from the Clearpath system. In order to validate the iPad, I followed the CAP process as outlined in Shah’s paper — my accuracy in reading glass slides versus WSI was >95% (and the <5% were trivial differences that would not have had clinical significance). I will not sign out a case, however, until the slide is reviewed on glass (see below).
The advantages of WSI are enormous: 1) If slides are not delivered on time, they can be initially reviewed electronically; 2) Retrieval of images and reports is instantaneous; 3) it is a wonderful teaching tool for the residents, as virtual dermatopathology will be used increasingly (if not exclusively) for board certifications.
The system is not perfect (although they’re striving to make it so). For example, I have trouble spotting eosinophils in inflammatory lesions, so I need to look carefully on TM for inflammatory lesions.
In a survey of 207 pathologists, 37% being board certified dermatopathologists, most respondents (77%) agreed that accurate diagnoses can be made with this technology, and 59% agreed that benefits of WSI outweigh concerns. However, 78% of pathologists reported that digital slides are too slow for routine clinical interpretation. The respondents were equally split as to whether they would like to adopt WSI (49%) or not (51%) (2).
According to Shah et al, “the Food and Drug Administration released technical guidelines for WSI devices, recognizing devices as class II (moderate risk), a significant change from the initially proposed class III (high risk).” When I informed CMS about my validation, I received a letter stating clearly that WSI, while promising, is still considered a research tool, and is not the standard of care for reimbursement. I cannot overemphasize the need to review slides by traditional glass microscopy at this time.
If that is the case, why do WSI? Because it is an opportunity to bridge dermatopathology’s past with its future. I have finally gotten my rhythm down with WSI. Occasionally I will preview some cases electronically, but I usually wait until I receive glass before I generate a report. After reaching my conclusion based on TM, I turn to the iPad, where I can review the image and generate my report. The turnaround time from the time of biopsy to written report (assuming no need for special stains or deeper sections) may be as quick as 72 hours – truly remarkable for a practice that outsources the technical component.
I edited a “Dialogues in Dermatology” discussion about 15 years ago regarding the pros and cons of digital versus film photography in dermatology. I imagine that some aficionados still use film (and maybe go into their dark room to develop it!) but I don’t know of any. Think about it — does your radiologist hold up a film to an X-ray box? It won’t be long before the microscope is a relic.
1. Shah KK, et al. Validation of diagnostic accuracy with whole-slide imaging compared with glass slide review in dermatopathology. J Am Acad Dermatol 2016; 75: 1229-37.
2. Onega T, et al. Use of digital whole slide imaging in dermatopathology. J Digit Imaging 2016; 29: 243-53.
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