Histopathology, Vol. 55, pp37-45, 2009 The definitive version is available at www.blackwell-synergy.com or:http: //onlinelibrary.wiley.com/doi/10.1111/j.1365-2559.2009.03325.x/abstract Tracking with virtual slides: a tool to study diagnostic error in histopathology Treanor D (1), Lim C (3), Magee D (2), Bulpitt A (2), Quirke P (1) ( 1 Abstract BACKGROUND: Diagnostic error in pathology is a significant problem. Studying the reasons for error is difficult because of a lack of data on the diagnostic process -virtual slides allow unsupervised study of diagnosis and error.METHODS: Software was developed to produce visualisations of the diagnostic track followed by pathologists as they viewed virtual slides. These showed the diagnostic path in 4 dimensions (x, y, time and zoom), areas studied for >1000ms, and included pathologists comments about the areas viewed. The system was used to study 2 trainee and 2 expert pathologists diagnosing 60 Barrett's oesophagus biopsies. Comparisons of the diagnostic tracks showed the reason for errors. RESULTS: 46 cases had an expert consensus diagnosis. The trainees made errors in 21 and 15 cases respectively, of which 11 and 9 were clinically significant. Errors were made across the whole spectrum of diagnoses from negative to intramucosal carcinoma.Detailed examination of the tracks showed that in all errors there was incorrect interpretation of information; in 3 errors there was an additional failure to identify diagnostic features.CONCLUSIONS: Tracking with virtual slides is a useful tool in studying diagnosis and error which has the potential for use in training and assessment.