Letters to the Editor
To the Editor:
The FDA recently approved Philips IntelliSite Pathology Solution (PIPS) as the first whole slide imaging (WSI) program for the purpose of diagnostic pathology.1 The PIPS system allows for glass slides of biopsied tissue to be transferred to a digital format and saved to a storage system at up to ×400 magnification. This FDA approval confers many advantages in the field of pathology and comes at a time when our society is increasingly digitized. Historically, WSI has been used mostly in medical education, research, archiving, and tumor board presentations, with little use in daily clinical practices.2
Among the benefits of the WSI system are the ability to read slides remotely, quickly receive second opinions, eliminate slide loss, prevent slide fading, and more effectively treat underserved communities. In a 2015 study by Onega et al assessing dermatopathologists' perceptions and use of WSI, it was found that only 41% of the 207 participants had experience with WSI, but 77% agreed that accurate diagnoses can be made with the use of digital slides. Some 59% felt the benefits outweighed the limitations of WSI. However, digital imaging was also reported by most participants (78%) to be too slow for routine clinical use which could limit its utilization despite the recent approval for WSI in primary diagnosis.2 Velez et al found in 2008 that microscope slide viewing was an average of 11 seconds faster than digital slide viewing, with the largest time difference for the least complex cases.3 In addition, the authors made particular note of the need for an improved navigation system to speed up the process. Another study comparing time to assess slides also agreed with the relative speed of glass slides versus digital slides, with average assessment times being 137.61 seconds and 176.77 seconds, respectively.4 However, with the recently approved PIPS system, it is reasonable to assume that increased familiarity will come with widespread implementation of WSI and that viewing time will decrease accordingly.
Aside from the perceived slowness of digital slide viewing, WSI seems to show great promise in its histological interpretation. In a study of 251 surgical biopsies, there was 96% concordance, or agreement, between glass and digital slide interpretation.5 Gilbertson et al also found that WSI allowed for successful diagnosis of not only the more simple cases but also complex pathology cases.6 In a recent study that we conducted comparing glass and digital slide interpretation, we found that for a given dermatopathologist, there was an 86.7% concordance rate for the diagnosis of spongiotic dermatitis versus mycosis fungoides on glass slides compared to digital slides. In addition, the rate of diagnostic disagreement between dermatopathologists was less for digital slides than it was for glass slides (13.3% and 20% respectively), indicating the WSI resulted in a greater degree of concordance for diagnosing dermatological cases. These findings are in agreement with the vast majority of validation studies in the literature, that WSI is equivalent, if not superior, to glass slides viewed through a light microscope.7,8
This FDA approval of PIPS and eventual widespread use of WSI will further enable teledermatopathology. The use of digital slides saved to a central system will enable rapid remote consultation of rural areas, preserve slides in their original viewing condition, and expedite getting a second opinion. This is of utmost importance considering the relatively limited number of dermatopathologists and increasing demand. Habeeb et al explored the success of WSI in Canada in an effort to further its implementation and eliminate the difference gap in care between urban centers and more distant communities. Canada has an 85% use of digital slides compared to the 41% reported in America.2 This study found a 96% concordance rate for routine cases and a 100% concordance rate for inflammatory and melanocytic biopsies,9 contrary to findings of other studies that neutrophils, eosinophils, and mitotic figures may be difficult to distinguish.10
Although diagnostic concordance rates between analog and digital slides range from 73% to 96.4% in the literature, it is worth pointing out that concordance is only an indirect measure of digital slide quality.9 There are other factors that come into play in making a diagnosis such as individual pathologist experiences, case history, and workstation monitor quality, among others. It is our opinion that the resolution of WSI is adequately sufficient to make an appropriate diagnosis and that any differences in interpretation are due to normal variations rather than a faulty medium of viewing. Furthermore, we are confident that with time and software improvement, the speed of use will be superior to even that of glass slides.
2. Onega T, Reisch LM, Frederick PD, et al. Use of digital whole slide imaging in dermatopathology. J Digit Imaging. 2016;29:243–253.
3. Velez N, Jukic D, Ho J. Evaluation of 2 whole-slide imaging applications in dermatopathology. Hum Pathol. 2008;39:1341–1349.
4. Vyas NS, Markow M, Prieto-Granada C, et al. Comparing whole slide digital images versus traditional glass slides in the detection of common microscopic features seen in dermatitis. J Pathol Inform. 2016;7:30.
5. Reyes C, Ikpatt OF, Nadji M, et al. Intra-observer reproducibility of whole slide imaging for the primary diagnosis of breast needle biopsies. J Pathol Inform. 2014;5:5.
6. Gilbertson JR, Ho J, Anthony L, et al. Primary histologic diagnosis using automated whole slide imaging: a validation study. BMC Clin Pathol. 2006;6:4.
7. Ho J, Pantanowitz L. Making pathology diagnoses with glass or digital slides: which modality is inferior? J Pathol Inform. 2017;8:14.
8. Shah KK, Lehman JS, Gibson LE, et al. Validation of diagnostic accuracy with whole-slide imaging compared with glass slide review in dermatopathology. J Am Acad Dermatol. 2016;75:1229–1237.
9. Al Habeeb A, Evans A, Ghazarian D. Virtual microscopy using whole-slide imaging as an enabler for teledermatopathology: a paired consultant validation study. J Pathol Inform. 2012;3:2.
10. Koch LH, Lampros JN, Delong LK, et al. Randomized comparison of virtual microscopy and traditional glass microscopy in diagnostic accuracy among dermatology and pathology residents. Hum Pathol. 2009;40:662–667.