Interobserver reproducibility of Gleason grading of prostatic adenocarcinoma among general pathologists

Context: Gleason grade is the most widely used grading system for prostatic carcinoma and is recommended by World Health Organization. It is essential that there should be good interobserver reproducibility of this grading system as it has important implications in patient management. Aim: To assess interobserver reproducibility of Gleason grading of prostatic adenocarcinoma. Design: A total of 20 cases of prostatic adenocarcinoma were scored using Gleason grade by 21 general pathologists. The scores were then compared using κ-coefficient and consensus score.
Results: For Gleason score groups (2-4, 5-6, 7 and 8-10) overall agreement with consensus score was 68%. Exact agreement for Gleason scores with consensus score was 43.3% and 92.3% within ±1 of the consensus score. κ coefficient for primary grade ranged from -0.32 to 0.92 with 60% of the readings in fair to moderate agreement range; and for secondary grade κ ranged from -0.30 to 0.62 with 78% of the readings in slight to fair agreement range. Kappa for Gleason scores ranged from -0.13 to 0.55 with 80% of the readings in slight to fair agreement range; and for Gleason score groups κ ranged from -0.11 to 0.82 with 68.5% of the readings in fair to moderate agreement range.
Conclusions: In our study interobserver reproducibility of Gleason scores among general pathologists was at lower level and it highlights the need to improve the observer reproducibility by continuous educational sessions and taking second opinion in cases where grade could significantly influence management.