Inter-reader agreement between expert and non-expert readers in the interpretation of placental MRI

To identify magnetic resonance imaging (MRI) features of placenta accreta spectrum (PAS) that are under reported in missed/under-classified cases, compare inter-reader agreement between subject matter experts (SMEs) and non-SME radiologists, and determine features most challenging for non-SME readers to detect.

In this IRB-approved retrospective study, 59 patients with pathologically confirmed PAS who underwent cesarean hysterectomy (2008-2022) and preoperative MRI were included. Cases were classified as missed/under-classified (n = 17) or concordant/over-classified (n = 42). Original radiology reports were reviewed for key PAS features. Missed/under-classified cases were reinterpreted by two SMEs and two non-SME radiologists using a structured template. Inter-reader agreement was assessed using intraclass correlation coefficients and kappa statistics.

Missed/under-classified cases had significantly fewer reported imaging findings than concordant/over-classified cases (1.5 vs. 3.4, p < 0.001). Secondary SME review increased reported findings per case (5.3, p < 0.001), identifying overlooked features including placental bands and myometrial thinning or bulging. SMEs demonstrated higher concordance but more overestimation of disease severity, whereas non-SMEs had higher rates of missed diagnoses (p = 0.01). Placental bands and myometrial abnormalities were challenging features for non-SME readers to report. SMEs maintained improved feature documentation despite concerns of perceived suboptimal image quality.

In a selected pathology-positive cesarean hysterectomy cohort, missed/under-classified PAS cases were driven by under reporting of key imaging features by non-SME radiologists, highlighting the need for targeted education and structured reporting. SMEs improve documentation of PAS features and may partially compensate for suboptimal image quality, underscoring the importance of access to expert review.