Rationale and Objectives
To evaluate interobserver agreement with the use of and the positive predictive value
(PPV) of Prostate Imaging Reporting and Data System version 2 (PI-RADS v2) for the
localization of intermediate- and high-grade prostate cancers on multiparametric magnetic
resonance imaging (mpMRI).
Materials and Methods
In this retrospective, institutional review board-approved study, 131 consecutive
patients who had mpMRI followed by transrectal ultrasound-MR imaging fusion-guided
biopsy of the prostate were included. Two readers who were blinded to initial mpMRI
reports, clinical data, and pathologic outcomes reviewed the MR images, identified
all prostate lesions, and scored each lesion based on the PI-RADS v2. Interobserver
agreement was assessed by intraclass correlation coefficient (ICC), and PPV was calculated
for each PI-RADS category.
PI-RADS v2 was found to have a moderate level of interobserver agreement between two
readers of varying experience, with ICC of 0.74, 0.72, and 0.67 for all lesions, peripheral
zone lesions, and transitional zone lesions, respectively. Despite only moderate interobserver
agreement, the calculated PPV in the detection of intermediate- and high-grade prostate
cancers for each PI-RADS category was very similar between the two readers, with approximate
PPV of 0%, 12%, 64%, and 87% for PI-RADS categories 2, 3, 4, and 5, respectively.
In our study, PI-RADS v2 has only moderate interobserver agreement, a similar finding
in studies of the original PI-RADS and in initial studies of PI-RADS v2. Despite this,
PI-RADS v2 appears to be a useful system to predict significant prostate cancer, with
PI-RADS scores correlating well with the likelihood of intermediate- and high-grade