Accuracy of Gleason grading by practicing pathologists and the impact of education on improving agreement

The aims of this study were to evaluate the accuracy of Gleason grading for prostatic adenocarcinoma among practicing pathologists in Japan and to determine the influence of education on this accuracy. Using a case-oriented approach, 16 hematoxylin and eosinstained glass slides with consensus scores established by 4 urologic pathologists were reviewed by 91 pathologists, divided into 2 groups. In group A, average agreements with consensus scores before and after an educational lecture were 55.7% (n = 17) and 68.4% (n = 25), and average kappa values were 0.43 and 0.67, respectively. Twelve pathologists reviewed slides twice in a different order, with average agreements of 59.5% and 77.6%, and average kappa values of 0.48 and 0.69 before and after the lecture, yielding a statistically significant improvement. In group B, the average agreement before providing an atlas with a tutorial was 61.3% (n = 61), and the kappa value was 0.44. In the second round, the average agreement was 74.5% (n = 39), and the kappa value was 0.68. Among 39 pathologists who reviewed slides twice, the average agreement in the first round was 58.8%, and the kappa value was 0.42. Improvement of both the average agreement and the kappa value were statistically significant. The average improvement in kappa values among participants who reviewed slides twice was 0.22 in group A and 0.27 in group B, a difference that is not statistically significant. Combining both groups, the incidence of concordant scores for 16 cases rose from 58.9% to 75.4%, an average increase of 16.5%. The undergrading of score 5-7 lesions was significantly reduced, from 36.3% to 14.2%. With respect to demographic factors, pathologists signing out more than 5000 cases per year showed a better agreement than those with more than 1000 cases per year (48.9% versus 78.8%; P = 0.031). These results indicate that the general agreement of Gleason scores among practicing pathologists in Japan was comparable with those in the Western countries as reported in the literature. Although this requires further improvement, both the lecture and the printed material had a similar influence on the degree of improvement.