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Background and Aims: Diagnosis of metabolic dysfunction‐associated steatohepatitis (MASH) requires histology. In this study, a magnetic resonance imaging (MRI) score was developed and validated to identify MASH in patients with metabolic dysfunction‐associated steatotic liver disease (MASLD). Secondarily, a screening strategy for MASH diagnosis was investigated. Methods: This prospective multicentre study included 317 patients with biopsy‐proven MASLD and contemporaneous MRI. The discovery cohort (Spain, Portugal) included 194 patients. NAFLD activity score (NAS) and fibrosis were assessed with the NASH‐CRN histologic system. MASH was defined by the presence of steatosis, lobular inflammation, and ballooning, with NAS ≥4 with or without fibrosis. An MRI‐based composite biomarker of Proton Density Fat Fraction and waist circumference (MR–MASH score) was developed. Findings were afterwards validated in an independent cohort (United States, Spain) with different MRI protocols. Results: In the derivation cohort, 51% (n = 99) had MASH. The MR–MASH score identified MASH with an AUC =.88 (95% CI.83–.93) and strongly correlated with NAS (r =.69). The MRI score lower cut‐off corresponded to 88% sensitivity with 86% NPV, while the upper cut‐off corresponded to 92% specificity with 87% PPV. MR–MASH was validated with an AUC =.86 (95% CI.77–.92), 91% sensitivity (lower cut‐off) and 87% specificity (upper cut‐off). A two‐step screening strategy with sequential MR–MASH examination performed in patients with indeterminate‐high FIB‐4 or transient elastography showed an 83–84% PPV to identify MASH. The AUC of MR–MASH was significantly higher than that of the FAST score (p <.001). Conclusions: The MR–MASH score has clinical utility in the identification and management of patients with MASH at risk of progression. [ABSTRACT FROM AUTHOR]

Summary: Background: Histological evaluation of metabolic‐associated fatty liver disease (MAFLD) biopsies is subjective, descriptive and with interobserver variability. Aims: To examine the relationship between different histological features (fibrosis, steatosis, inflammation and iron) measured with automated whole‐slide quantitative digital pathology and corresponding semiquantitative scoring systems, and the distribution of digital pathology measurements across Fatty Liver Inhibition of Progression (FLIP) algorithm and Steatosis, Activity and Fibrosis (SAF) scoring system Methods: We prospectively included 136 consecutive patients who underwent liver biopsy for MAFLD at three Spanish centres (January 2017‐January 2020). Biopsies were scored by two blinded pathologists according to the Non‐alcoholic Steatohepatitis (NASH) Clinical Research Network system for fibrosis staging, the FLIP/SAF classification for steatosis and inflammation grading and Deugnier score for iron grading. Proportionate areas of collagen, fat, inflammatory cells and iron deposits were measured with computer‐assisted digital image analysis. A test‐retest experiment was performed for precision repeatability evaluation. Results: Digital pathology showed strong correlation with fibrosis (r = 0.79; P < 0.001), steatosis (r = 0.85; P < 0.001) and iron (r = 0.70; P < 0.001). Performance was lower when assessing the degree of inflammation (r = 0.35; P < 0.001). NASH cases had a higher proportion of collagen and fat compared to non‐NASH cases (P < 0.005), whereas inflammation and iron quantification did not show significant differences between categories. Repeatability evaluation showed that all the coefficients of variation were ≤1.1% and all intraclass correlation coefficient values were ≥0.99, except those of collagen. Conclusion: Digital pathology allows an automated, precise, objective and quantitative assessment of MAFLD histological features. Digital analysis measurements show good concordance with pathologists´ scores. [ABSTRACT FROM AUTHOR]