Inter-reader Agreement for CT/MRI LI-RADS Category M Imaging Features: A Systematic Review and Meta-analysis.

Backgrounds/Aims To systematically evaluate inter-reader agreement in the assessment of individual Liver Imaging Reporting and Data System (LI-RADS) category M (LR-M) imaging features in computed tomography/magnetic resonance imaging (CT/MRI) LI-RADS v2018, and to explore the causes of poor agreement in LR-M assignment. Methods Original studies reporting inter-reader agreement for LR-M features on multiphasic CT or MRI were identified using the MEDLINE, EMBASE, and Cochrane databases. The pooled kappa coefficient (κ) was calculated using the DerSimonian-Laird random-effects model. Heterogeneity was assessed using Cochran's Q test and I2 statistics. Subgroup meta-regression analyses were conducted to explore the study heterogeneity. Results In total, 24 eligible studies with 5,163 hepatic observations were included. The pooled κ values were 0.72 (95% confidence interval, 0.65-0.78) for rim arterial phase hyperenhancement, 0.52 (0.39-0.65) for peripheral washout, 0.60 (0.50-0.70) for delayed central enhancement, 0.68 (0.57-0.78) for targetoid restriction, 0.74 (0.65-0.83) for targetoid transitional phase/hepatobiliary phase appearance, 0.64 (0.49-0.78) for infiltrative appearance, 0.49 (0.30-0.68) for marked diffusion restriction, and 0.61 (0.48-0.73) for necrosis or severe ischemia. Substantial study heterogeneity was observed for all LR-M features (Cochran's Q test: p < 0.01; I2 ≥ 89.2%). Studies with a mean observation size of <3 cm, those performed using 1.5-T MRI, and those with multiple image readers, were significantly associated with poor agreement of LR-M features. Conclusions The agreement for peripheral washout and marked diffusion restriction was limited. The LI-RADS should focus on improving the agreement of LR-M features.