Intraobserver and interobserver agreement of the American College of Radiology PI-RADS 2.1 score

Background: Magnetic Resonance Imaging (MRI) of the prostate is a key diagnostic tool for identifying prostate carcinoma. The Prostate Imaging-Reporting and Data System (PI-RADS) scale is the standard system for interpreting these images. Standardizing and evaluating this scale is crucial for ensuring consistent and reproducible results.
Objective: This study aims to assess both the interobserver and intraobserver agreement of the PI-RADS version 2.1.
Material and methods: In this retrospective observational study, 129 prostate MRI scans from patients with suspected prostate cancer were evaluated. Three radiologists, each with different levels of experience, analyzed these scans at two separate times using the PI-RADS 2.1 scoring system. Both intraobserver and interobserver agreements were measured.
Results: The study found substantial interobserver agreement (kappa > 0.6) across all categories, with category 5 showing the highest level of agreement. Intraobserver reproducibility was also high, with the highest kappa value reaching 0.856. Further analysis based on the radiologists’ years of experience revealed significant interobserver agreement in all instances.
Conclusions: The PI-RADS 2.1 classification system demonstrates high reproducibility across different categories, particularly for lesions more likely to be clinically significant cancers. This underscores its reliability in varied diagnostic scenarios.