Validation of Multiple Whole Slide Imaging Scanners Based on the Guideline From the College of American Pathologists Pathology and Laboratory Quality Center

CONTEXT: Whole slide imaging (WSI) produces a virtual image that can be transmitted electronically. This technology has clinical applications in situations in which glass slides are not readily available. OBJECTIVE: To examine the results of a validation study performed using the draft version of the WSI clinical validation guideline recently released by the College of American Pathologists. DESIGN: Ten iScan Coreo Au scanners (Ventana Medical Systems, Tucson, Arizona) were validated, 6 with one set of 100 cases and 4 with a different set of 100 cases, for 1000 case examinations. The cases were selected consecutively from the following case types: internal consultations and malignancies and cases with frozen sections, special stains, and/or immunohistochemistry. Only key slides were scanned from each case. The slides were scanned at ×20 magnification. Pathologists reviewed the cases as both glass slides and WSI, with at least a 3-week washout period between viewings. RESULTS: Intraobserver agreement between glass slides and WSI was present for 786 (79%) of the 1000 cases. Major discrepancies occurred in 18 cases (1.8%). κ statistics compiled for the subset of cases (n = 504; 50%) with concern for neoplasia showed excellent agreement (κ = 0.8782). Individual scanners performed similarly to one another. Analysis of the results revealed an area of concern: small focal findings. CONCLUSIONS: The results were felt to validate the use of WSI for the intended applications in our multiinstitutional laboratory system, although scans at ×20 magnification may be insufficient for cases hinging on small focal findings, such as microorganisms and inflammatory processes.