TABLE 1.

Strong recommendations (SRs) and good practice statements (GPSs) from the 2021 College of American Pathologists guideline for validation of whole slide imaging systems

Item	Description
SR 1	The validation process should include a sample set of at least 60 cases for one application, or use case (e.g., haematoxylin–eosin–stained sections of fixed tissue, frozen sections, haematology), that reflect the spectrum and complexity of specimen types and diagnoses likely to be encountered during routine practice. The validation should include another 20 cases to cover additional applications such as immunohistochemistry or other special stains if these applications are relevant to an intended use and were not included in the 60 cases mentioned above.
SR 2	The validation study should establish diagnostic concordance between digital and glass slides for the same observer (i.e., intra‐observer variability). If concordance is less than 95%, laboratories should investigate and attempt to remedy the cause.
SR 3	A washout period of at least 2 weeks should occur between viewing digital and glass slides
GPS 1	All pathology laboratories implementing WSI technology for clinical diagnostic purposes should carry out their own validation studies.
GPS 2	Validation should be appropriate for and applicable to the intended clinical use and clinical setting of the application in which WSI will be used. Validation of WSI systems should involve specimen preparation types relevant to intended use (e.g., formalin‐fixed, paraffin‐embedded tissue; frozen tissue; immunohistochemical stains). If a new application for WSI is contemplated, and it differs materially from the previously validated use, a separate validation for the new application should be performed.
GPS 3	The validation study should closely emulate the real‐world clinical environment in which the technology will be used.
GPS 4	The validation study should encompass the entire WSI system. It is not necessary to separately validate each individual component (eg, computer hardware, monitor, network, scanner) of the system or the individual steps of the digital imaging process.
GPS 5	Laboratories should have procedures in place to address changes to the WSI system that could impact clinical results.
GPS 6	Pathologists adequately trained to use the WSI system must be involved in the validation process.
GPS 7	The validation process should confirm all of the material present on a glass slide to be scanned is included in the digital image.
GPS 8	Documentation should be maintained recording the method, measurements, and final approval of validation for the WSI system to be used in the anatomic pathology laboratory.
GPS 9	Pathologists should review cases/slides in a validation set in random order. This applies to both the review modality (ie, glass slides or digital) and the order in which slides/cases are reviewed within each modality.