Validation of a whole slide imaging system for primary diagnosis in surgical pathology: A community hospital experience

Guidelines for validating whole slide imaging (WSI) for primary diagnosis in surgical pathology have been recommended by an expert panel commissioned by the College of American Pathologists. The implementation of such a system using these validation guidelines has not been reported from the community hospital setting. The objective was to implement a WSI system, validate each pathologist using the system and run the system in parallel with routine glass slide interpretation. Six pathologists re-reviewed approximately 300 previously diagnosed specimens each, divided equally between glass slides and digital images (scanned at ×20). Baseline intraobserver discordance rates (glass to glass) were calculated and compared to discordance rates between the original glass slide interpretation and the reviewed digital slide interpretation. A minimum of 3 months was used as the washout period. After validation, a subset of daily cases was diagnosed in parallel using traditional microscopy (TM) and WSI over an 8-month period. The TM and WSI discordance rates ranged from 3.3% to 13.3% and 2.1% to 10.1%, respectively. There was no statistically significant difference among the pathologists. The parallel study yielded similar rates of discordances. In our laboratory, after appropriate implementation and training, there was no difference between the WSI and TM methods.