The Critical Need to Expand Proficiency Testing to Cover Telepathology

To the Editor.—In current pathology practice, laboratory proficiency testing (PT) is the standard of care for most clinical laboratory testing.^1,2  PT is a critical external quality assessment involving unknown specimens that are sent to clinical laboratories to help verify that the laboratory test results are accurate.^1,3  The concept of PT was initiated when a group of pathologists found it disturbing to know that a divided blood sample analyzed in 2 clinical laboratories resulted in widely divergent results. Because of the recognition of this concept, the Clinical Pathology Section of the Philadelphia County Medical Society began the very first PT for clinical laboratory tests in the United States by distributing unknown serum specimens among their members to report at the following meeting.^1–3  The results of the second such PT and survey of the members of the newly formed Pennsylvania state pathology society in 1946 highlighted the value of PT in uncovering inaccuracies in clinical laboratory testing that occurred even with the internal quality control in each laboratory.³ 

Telepathology, or effectively the practice of pathology at a distance through telecommunication links, which has also been referred to as digital pathology, has been a recent major innovation that is increasingly being used to improve the efficiency and quality of the practice of pathology, though there are barriers to overcome, such as a relative lack of standards compared to other fields of pathology.⁴  Since the introduction of the term telepathology in 1986, strides have been made in the creation of some of the clinical standards for the use of this modality, similarly to how strides were made in the improvement of clinical laboratory testing in the 1940s. This includes not only guidelines on internal quality assurance and quality control, but also guidelines on the validation of whole slide imaging (WSI).^4,5 

However, similar to the situation in the past, there currently exists no established external PT program for telepathology. Instead of an external PT program to assess the accuracy of the diagnoses, there is currently an educational College of American Pathologists (CAP) program that is part of CAP’s WSI quality improvement program. It focuses on the technical component of WSI production (assessed only after the scanned image is transferred to Digitalscope on the CAP’s server). This program does not assess the accuracy of the diagnoses or assessments of biomarker analyses (estrogen receptor, progesterone receptor, proliferation index, programmed death ligand-1, etc) made from these digital slides, nor are the slides treated in exactly the same manner as patient specimens, as the diagnoses are known up front and the same digital platform is involved, which may not also be used for patient care at different institutions.^6,7  A PT program for telepathology that includes external assessment of the diagnostic accuracy from digital slides, including biomarker assessments, would be an important improvement in the practice of telepathology across institutions. Although there is an existing educational CAP program, there is no specific PT program geared toward telepathology. It would be important to have telepathology-specific PT, including but not limited to surgical pathology, telecytology, and frozen section, because telepathology has been used extensively and widely. We suggest having a PT schedule of 5 cases 3 times a year for real-time monitoring to ensure we embrace this highly useful technology safely, similar to the current 2024 educational programs by CAP.⁸ 

Today we know that digital (tele)pathology is the emerging powerful modality. This modality is rapidly being incorporated in clinical decision-making for rapid on-site specimen evaluation, frozen sections, and primary diagnosis. A sample of the modality of telepathology (Figure, A and B) is demonstrated by 2 WSIs. The CAP now has checklist items for laboratories using digital pathology to build a quality assurance process. Recently on the CAP 2023 Practice Leader Survey Report, nearly a third, or 30%, of practices already performed remote sign-out, with an additional 11% planning to implement this within the next 12 months.⁹  This means that within a year of the survey, or in this year 2024, nearly half, or 41%, will have adopted telepathology. To report this additional clinical work, there are additional preliminary Current Procedural Terminology codes that are currently under review.¹⁰  Although the field of telepathology is indeed growing in leaps and bounds, there is no PT program that distributes unknown glass slides to institutions using telepathology for the specific purpose of being scanned or placed into the telepathology workflow to be read like a patient specimen for the purpose of external quality assurance. Instead, each laboratory using telepathology (like the clinical laboratories’ testing of clinical analytes in 1945) and following the published telepathology guidelines is currently using internal quality assurance measures to best ensure quality patient care and diagnosis given the available tools.^3–5  It is critical that this be developed to standardize the process and review as it will also determine if the instrumentation is working as it is intended to and the review process is accurate. This also will fulfill the requirement for the telepathology checklist to have a quality parameter that is implemented by a laboratory.

Fortunately, progress in testing quality has arched toward improvement. The survey by Belk and Sunderman³  played a key role in motivating the passage of the Federal Clinical Laboratories Improvement Act of 1967, and nowadays, the use of PT for most clinical analytes is well established. To the end of improving the practice of telepathology, the CAP should endeavor to establish a PT program involving unknown glass slides to be sent to telepathology practices so that PT of the whole practice of telepathology (from slide scanning through digital or remote viewing and telediagnosis) can be externally assessed to be accurate for best and safe patient care.